To answer both your questions in one post:
This game is 100% complete! Any updates are bug fixes unless otherwise noted. It will be on Steam, but expect that to be a month or so out, since the approval process for Steam is a lot longer than usual.
You will stay in the form that enemies TF you into after battle, but you can always switch back in the menu or by using the hotkeys ("A" and "S"). The dialogue changes in a couple of spots based on your current form. Each form has plenty of unlocks, and even a new combination skill to unlock once you learn enough from each skill tree.