I'm conjecturing the guys got Walter Peck fired from the EPA. He'd have to be angry about that, and he'd find a new way to continue his vendetta against Venkman and the guys.
As for Peter and Dana breaking up, I think it happened after Peter introduced her as the old ball and chains. :p :-) Then Dana married Andre Wallance, A.K.A. “The Stiff”. By 2008, they have a child, Oscar Wallance.
Of course that may be subject to change. We don't even know if 88mph Studios is going in the direction of GB II. Someone said that they weren't going to do GB II in the new comic's universe. But I'm hoping they're wrong. I'd like to see GB II, but only if they change it to fit in with the first movie more. I don't want to see a recycled plot that's like a live-action cartoon. Maybe the guys could've stayed in business, and wouldn't have gotten nearly sued out of existance. And none of that kiddie Slimer/Louis nonsense. That was TOO cartoony. Especially the deleted scenes of them together. I'm glad they didn't add that stuff in. I wouldn't won't to see that in this comic. :p