You didn't miss anything so far. One thing I can mention is the alpha releases are basically an introduction of all characters into the game. There are three remaining characters, Astrid should come out next week (I hope), Riley, then Lauren coming next. After all characters are introduced, their story will progress from there.
As for the bad ending, the main one is you have to screw up your relationship with each girl to trigger it. I may add a few minor bad endings by death if you are too adventurous; however, those deaths will be purely accidental, but can be easily avoidable. I will post a devlog about the bad endings in the future.