Revan doesn't help the LS Protags any more than Satele helps the DS Protags. That is to say, not at all. The Outlander is just visualizing himself as Revan and using his dark side powers, which strikes me as particularly weird rather than particularly cool. It does support my SOR Revan = Dark Side narrative, though, so I'm not really complaining.
Still, Valkorion was killed by the Eternal family and the Outlander. Revan got ditched in SOR. It's time to cope.
He did. NewGuy is wrong.
The Outlander can't magically imagine powers for himself. Combat within the dream realm is a reflection of physical reality. The instance of his will changing reality was when willpower was actually in question. The Outlander could decide Valkorion was chained to the phrase since Valkorion's full consciousness was within the Outlander.
Revan and Satele Shan used the Force, presumably via meditation, to passively aid the Outlander in their fight, granting him additional weapons and abilities. They were not fully present, but they were working through and with the Outlander.