Not sure what you mean about unlocking the demesnes, sorry - you can already wander around them once you hit love 4 with the demesne's owner.
The 5th heart is the final heart that you can only unlock by doing a special event for each girl in Act Three (not implemented yet, though!)
Nothing in the game is behind a paygate - everyone, whether you pledge $100 or $0 gets access to exactly the same game.
Yes, Chloe will be using her alternate forms (and gaining some new ones) a lot more in Act Three! I even built a mini-system into the combat system just for her shifting :)