Correct me if I'm wrong but didn't tychos loyalty come into question in the EU stories?

Yes it was in question in the first two or three books from the x-wing series, later on in series he was cleared of any accusations

Was it because he was ok shooting revel captives?

It was because Tycho WAS a Rebel Captive

Tycho loaded and Jake Loaded with any action sharing becomes a very good list. Not quite enough uumph to really be competitive but with Outmanuever and PTL they certainly make it an interesting game.