Your stat system seems a little clunky, and the math and bonuses feel weird.

Have you considered Risus? It can be read in five minutes. It only takes a second to set up a character, and conflict resolution is as simple as rolling the requisite number of d6's. It's an extremely flexible system that allows massive variation in players while still having a fair conflict resolution and degrees of character specialization. I've actually run games with this and it's probably the best system to use for a play by post.

http://www.systemreferencedocuments.org/resources/systems/pennpaper/risus/risus/index.html?1