I think that the Republicans in congress, regardless of whether they stick with Trump or go off on their own are going to continue to behave, exactly, like they have insofar as how they vote and behave. I don't see that changing no matter what happens. The only difference is that the Trumpites will continue lying and hating with vigor whilst the rest will, pretty much just keep on going.
The real problem is that most sitting Republicans need the 'base' to get elected and the base is ruled by Trump. As far as I can tell, all sitting Republicans are willing to do just about anything to keep their jobs. That being the case they are unlikely to upset Trump and all the talk of a new party just ain't gonna happen and it won't make any difference anyway.
Its kinda like the Bernie supporters and the Democratic party. Pretty much the same environment without the utter meanness.