Summary:
Can I program a \"thick client\" game in C without reinventing wheels, or should I just bite the bullet and use some libr
I would recomend you try pyglet.
Do some tests, see if you can make it fast enough for you. Only if you prove to yourself that it's not move to a lower level. Although, I'm fairly confident that python + pyglet can handle it... at worst you'll have to write a few C extensions.