Chatwood has still walked about 4 batters per 9 IP away from Coors in his career. I'm skeptical he's going to improve on his away-from-Coors numbers just because he's no longer pitching half his games at Coors.
Only six pitching staffs had worse BB% than the Cubs this year: Orioles, Braves, Marlins, Mets, Reds, and White Sox. Those were also 6 of the worst 7 teams in team ERA, and 6 of the worst 10 in fWAR. In general, pitching staffs that can't throw strikes are bad. The Cubs really need more strike throwers, and Chatwood doesn't help.