Sorry for the late reply, I just now saw this!
In story mode, Sterling has an ending but his path only has 3 short scenes so it's not worth it really and I consider it a bad ending. In open mode, you can date Faust, Wizz, Collin and Seth but only Faust and Collin are released right now.
I was a complete train wreck writing Dallas path. >_>
No, there is not a good/bad ending. You can reach the AMPs without completing a romance so I guess that's a bad ending. (And like I said, Sterling is not a happy ending.) All band have to leave because of Open Mode - Robin has to start a new band. They'll come back, but not as band members.
Emmitt is especially hard to raise stats on because of his personality, but it is definitely possible. It gets easier to raise stats the higher your stat is ... sort of a Catch 22, but it should get easier eventually. Buying equipment from the store gives everyone a base stat boost, which should make it even easier.
I know what you mean about "early access" and games that say they're "beta" but aren't finished. Story Mode is complete, I'm just adding DLC to open mode. :)
Your post was a pleasure to read. Glad you're enjoying the game. Have fun!!