Ok so here's the contents and summary of the section on the 6th commandment. Something our generation, which has been MKULTRA'd by pornography and the general hypersexualised culture really need to pay attention to because we need to see just how much damage has been done.
Contents: (I'll summarise some/most of these but not all here): 
413. First, the Dr implores us to forgive him if we find his detail of the treatment on this matter disturbing or disgusting but stresses its importance because of it being such a common source of becoming damned.
He explains the distinction between 'sensitive enjoyment' (where you enjoy a thing because of the delicacy of a feeling of a touch, as of silk or a rose), and sexual/carnal enjoyment (where you enjoy a thing because of an instinct that ends in insemination naturally) - e.g. (...)
A father has a natural love for his son and kisses his cheeks or forehead. This isn't sinful at all; there is a natural love between the two whereby these acts of sensible pleasure out of affection are exchanged, and there is no sexual dimension to the delectation.
414: While the commandment mentions the greek word 'moicheia' in the Septuagint, it is proven from Augustine and Ambrose that all sexual acts outside of marriage are forbidden by the same precept.
i.e. while fornication is less bad than adultery, the carnal act is ordered to matrimony (by which children are begotten and educated), and so all carnal acts are ordered to this end.
Lastly, the Doctor quotes other theologians:
415. On whether paucity (smallness) of an act is granted in order to reduce the gravity in lustful matters. The distinction earlier made between sensitive and carnal enjoyment is mentioned - however, keep attention. The distinction rarely applies.
Q1 - can paucity be granted in any sexual matter with a non-spouse? The Dr says no, as every small enjoyment of the kind is a grave evil, but general 'lust' (simple inordinate/excessive enjoyment of the sense of touch) can be venial.
He says however that every carnal *or lustful* delectation taken with full knowledge and deliberation (full consent of the will stated in technical terms) *is* mortally sinful due to the attached papally condemned proposition:
to break this down: it is not the case that a kiss performed for the reason of an intent to gain carnal and sensible delight from it is only venial; it is mortal *even if* you exclude any danger of pollution (ejaculation) or a consent to further and less minor sexual enjoyments.
The reason is that every carnal enjoyment is an 'arousal of the spirits serving generation'; that these are 'inchoate (semiformed) pollutions' as they are acts that lead toward and tend naturally towards eventual insemination as their purpose is to romantically/sexually bond.
He quotes several theologians and argues that the acts related are condemned - 'namely to pinch the hand of a woman, to intertwine fingers, etc., as a mortal sin due to the carnal enjoyment which then takes place, or at least on account of the proximate danger of it.'
Q2. On whether paucity is granted for simply sensible/natural enjoyment, if one receives such a delectation from touching a woman's hand 'as they are from a delicate thing, say a rose, silk garments?' He says no -
reasoning that touches are enjoyable according to the sense of the touch of one of the sex + age we are attracted to is per se ordered to pollution, and cannot be distinct in such a case from pure sensible enjoyment due to our fallen, concupiscential nature -
and that it's a mortal sin to expose yourself to the danger of consent to carnal enjoyment.
He gives 1 exception where delectation is not sought deliberately by an action that is a gesture due by some duty, but where it is experienced nonetheless - though after knowing the act causes delectation it must be abstained from thereafter, and the delectation must be detested.
He quotes several theologians as follows.
417. Kisses, even those done due to the custom of one's country, if they happen a. for a space of time or b. with vehemence, are ordinarily mortal - definitely kisses on the mouth or the involvement of the tongue.
422. While in principle it's possible to look at the non-private parts of a beautiful person of the opposite sex to appreciate said beauty without incurring any sin, in practice it's rare a person doesn't fall into at least venial sin - but if frequent, he can't be excused at all
424. It is impossible to look morosely, especially at obscene images of the sex of your attraction without incurring mortal sin, unless over too great a distance and too short a time for lustful intent.
425. Women's adornment - for what is necessary for the decency of her status or the custom for what is necessary to be presentable in her country - is permissible, as well as to please a spouse, and in a limited way to find a future spouse.
However - if adornment is ever done with the intent of levity of vanity then it is venial, and if for attracting carnal attention from men in general or particular men/a particular man then it is mortal. This includes makeup - ok for presentability + spouse, not otherwise.
Due to the custom - such as some places in africa where women do not cover breasts - it isn't necessarily mortal to uncover some part of the self or to use beyond basic makeup, but can still be venial as they can inherently lead to scandal.
While the ideal is to move away from this and toward full Marian imitation, the minimum practice to be enjoined (besides not exposing genitalia) is to be defined by the ecclesial authority for the slow improvement toward that ideal.
Foul words, reading of obscenities, watching foul arts (movies or plays), perverted songs, deeds, letters and amorous gifts, if only done out of curiosity or vain consolation are not mortal, but if with a sexual end or the realisation of the danger of spiritual ruin, are mortal.
426: It is not inherently evil to mention or hear foul words for example to mention what has been heard to you, the morality depends on the end whereby the words are mentioned.
To speak foul words out of vain consolation or a joke is venial in itself, but if you know those listening are weak in spirit so as to be scandalised, if there is deliberate delectation in their foulness, or if the words are very lustful in their signification, it is mortal.
It is mortally sinful to speak foul words
1. Due to the delectation taken from the thought of the foul things signified by the words.
2. In front of girls and women (aside from a spouse whereby there is good and natural sexual delectation).
3. Where scandal is known to be likely
1. Due to the delectation taken from the thought of the foul things signified by the words.
2. In front of girls and women (aside from a spouse whereby there is good and natural sexual delectation).
3. Where scandal is known to be likely
To detail (2) - it is mortally sinful to name shameful things or discussing with foul words or with delectation or the intent to cause lustful thought the manner of sexual intercourse or other sexual acts in the presence of adolescents and young women especially of upright life.
It is further mortally sinful to detail one's own foul sins with the intent to boast of them.
On foul plays - unless one is very weak, there is no mortal sin if the it isn't notably foul. If notably foul things are shown in a foul manner, it is mortal to watch to seek delectation, but venial if out of curiosity, excluding knowing consent to danger of foul delectation.
If someone provides money or applause without which the play or movie would not have been performed/made, then doing so is mortal. Failing to prevent or suitably impede such a play when possible due to one's office is also mortal.
Those putting on or composing these plays/movies, when notably foul, sin mortally due to scandal to viewers even if unintended to cause the scandal due to the sin incurred by those involved in the representation itself.
429. Dances are lawful if out of joy and not lust. Lustful dancing is an abuse of a good act. Dancing with women with only a light touch of the woman's hand is either simply venial, due to scandal to others even if unintended, or not sinful at all depending on extent.
431. The betrothed are in the same state as any other pair of unmarried men and women with no change, and as before if a sensible delectation is experienced and it is realised that this is indistinguishable from carnal delectation it is obligatory to abstain but not before.
A married person cannot engage in relations with their spouse primarily or entirely for the purpose of deriving physical pleasure for self gratification whether or not the spouse does the same - it must be out of marital love *and* open to the manifestation of this as new life.
To recap - holding your unwedded partner's hand is not inherently sinful. If you have just cause or no sensory enjoyment, it's fine - if the intent is to receive some kind of sensory enjoyment, this is venial due to lack of intent to risk or directly to receive sexual enjoyment.
If you're making physical contact *knowing* the risk of an indistinguishable sexual enjoyment (however minor) without just cause for the contact, or indeed seeking that minor sexual enjoyment out directly, then it becomes mortal. Otherwise you can do it but it's best not to.
