Quite frankly, you aren't going to solve 500 and database errors on (what I assume is) a bog-standard cheap shared web host. You don't have the control over the environment that you need.
Actually, I'm already on a dedicated server. A low end one, but yeah. Ajax for the character pane is interesting ... honestly, I haven't spent enough time with it yet (see chat). Among other things, less flickeryness might be nice, though.