Fair warning: I have neither the time nor inclination tonight to do Texas law research, so I'm going to be going on a broad view of the subject.
In most of the world, the loser pays the winner's attorneys' fees. In the USA, the rule is that each side bears its own fees win or lose.
Anti-SLAPP laws, as a rule, have such provisions. This is certainly true in Texas.
For full fees - which we know Marchi gets - Sam's job is to show the court that his hourly is reasonable, and the time spent was reasonable. Or be embarrassed when the court tells him what was reasonable.
Here, I have relatively little experience, so I'm sure that Akiva, Lane, T-dot, and basically everyone else will be along to tell me I screwed up shortly. (This is part of the reason I'm looking to err low.)