I thought it was pretty straightforward. If you did things right, you'll end up at the crossways between sacrificing your gonads for immortality, or sacrificing your life so your children can have functional gonads.
Then you'll have to survive the midget-mechanic's adoptive daughter after she realizes she was supposed to be a princess (which, I don't know why, but she had every other reason not to go kamikaze mode and might as well fuck one of your children, but okay), and after that, you'll do either procedure.
Alison ending, I think, is when you die (or something along the lines of losing :P) at the undead island place, and then you're given three choices :
1. Fight against Death, and get rekt.
2. Accept Death, and get sent to Life #2 with Alison.
3. Bargain with Death, and become his lackey as an immortal fighter.