Be careful with the bench. Individual dumbbells are better than a stratght barbell, but neither are "ideal" for pitchers. You actually can do quite well with push-ups. I know they're not glam, but they work.
Also, what kind of work are you doing to offset the chest development? Anything for your upper back or scapular muscles (shoulder blades)? It's always important to work both sides of the body equally, especially for an activity such as pitching, where one muscle tweak can put you on the DL.
My TUFFCUFF program, out shortly, addresses scapular stabilzation at length and provides numerous exercises (including different dumbbell benches) to build more balanced strength.
Let us know how your strength training goes.