I still remain skeptical about any of the specific claims, because many of these things would be impossible to verify. Or rather impossible, barring the video evidence that apparently Putin has (if it exists).
That said there are several factors that make it likely that at least some, if not the entirety, of these documents are true:
This was in the official briefing.
The Trump and Trump surrogate ties to Russia are well documented and verified.
That Trump and his campaign exercised influence to alter stances towards Russia, and in no other manner modified the GOP platform is established fact.
Trump has repeatedly and consistently praised Putin, without reservation. He has criticized damn near everyone else.
Though we can not know the full extent and nature of them, we can be quite certain that Trump has financial ties to Russian oligarchs. How deep, how shady? No way to know currently.
Trump is an unhinged megolomanical ego tripping asshole.
Trump is using Russian sources to try and claim these are false rumors.
Trumps response has been uniquely unhinged. It is certainly not the response of an innocent man.
Again, do I think every claim is true? Eh, quite possibly no. Do we know if any specific claims are true? That is hard to determine, though certainly some would be easier than others. And as far as claims go?
This is honestly the least damning, but by far funniest, claim there. I honestly don't personally care if it is true or not, on the list of bad Trump things, this wouldn't register. It is, however, a comedy gold show... mine. Gold. Mine. Peese excuse me, this is a weird situation urine. That was a typographical pisstake. They've been leaking out lately.