Hmm, you're right, the feet are a little small. It would definitely have to bend its leg joints every time it takes a step in order to dissipate the weight. That's why that kind of leg is a lot slower..
The gun might be pretty large overall, but the individual firing chambers are pretty small, so I don't think recoil would be a big problem, but sometimes I do put bigger cannons up there, and maybe I should keep recoil in mind more often. Give it some shock absorbers... yeah
Thanks for the insightful comments!
(oh, and that IS the thorax)