1) While there isn't any solid evidence, several things imply that Revan at least practiced Jar'Kai. First off is the concept art, second is the illusion. While I agree that the concept art isn't much, wasn't the illusion based on the Revan that the Exile knew? I haven't played it in a while, so I'm a little sketchy on the details of that cave. There are some things pointing against this though.
- In all of the story sequences of the first game, Revan is shown wielding a single blade...Not something Jar'Kai does, unless I'm mistaken.
- Once again, in the comic where someone has a vision of Revan (I think it was one of the Qel-Droma characters...) standing above the defeated Malak, he's once again wielding a single blue saber.
Of course, it's hardly impossible that he'd learn more than one style.
2) We have nothing showing that Revan got the Holocron. It's possible that he gave it to Uthar for prestige. It's also possible that he just didn't do it. IIRC, even Kreia said that nobody had any idea what happened to the artifacts of the tombs. Plus, did it ever actually say the Sith Holocron they found in the Tomb was about his saber abilities? Can't remember...
3) When was it said that he knew Juyo? I haven't seen much that his single-bladed style resembles.