1) Parts of Steele Dossier (like Cohen in Prague) are probably false, but
Trump lied about "no deals with Russia" and knew that both Cohen and Trump Jr lied about Trump Tower Moscow negotiations to Congress.
Trump told Cohen to lie to Melania about hush fund payments to Stormy Daniels
Cohen thinks Trump's not under audit and is hiding the fact that he's underpaid his taxes
but Trump knew about, and directed, hush fund payments to mistresses, took efforts to hide them, and failed to report his debt to repay Cohen for them.
Trump thought he probably wouldn't win (like most pundits) so had strong financial incentive to please Russia and land the Trump Tower Moscow dea.
Trump knew Don Jr, Roger Stone, and Paul Manafort were trying to assist Russian attacks on US elections and seeking to benefit from those attacks.
Donald Trump has done dishonorable things. He's in the White House.