I think Gaston would have been a good main character for a hypothetical Beauty and the Beast sequel (or a good D&D PC). He's the inverse of the standard hero - rather than starting out weak but pure of heart, he starts out strong, clever, brave, and charismatic, but also a rotten person. However, he just crossed several lines in a row (literally stabbing someone in the back is pretty bad even by his own standards), nearly died (Disney characters routinely survive falling off of cliffs), and can't go home to a town where everyone knows he's a villain. Can he turn his life around after hitting rock bottom (both literally and figuratively)?
I'd play him as a paladin, for that strength/charisma combination. Maybe he was saved through divine intervention? That could be enough to make him change his ways. A combat-oriented bard might work too; he does sing...
Same witch that did Beast's curse is the one who saved Gaston.
You have a year to prove you're not a piece of shit or you die.
She doubles as a quest giver. "Here's a couple quests. Pick one and do it. Every time you help someone you prove you're a little less awful, and every time you ask me if you've done enough to be saved, you lose a few points of redemption credit, so don't ask me if you've been good enough to not die. Get to cracking on these heroic deeds, chop chop."
Make a few of the tasks morally complicated.
Make all of them take measurable time. Sure, rounding up sheep for the farmer isn't too dangerous, but it'll take you a while and it's not as heroic as fighting that necromancer... which task do you take?
When I was a lad I had two dozen health, in encounters to help me tank hiiiits!
But now that I'm grown, I have twelve dozen health, so I pretty much don't give a shiiiit!