Not much gain with the 225's, and the wheels (7.5) are too wide. I do not know if the 265's are too wide for the 7.5 wheels. I suggest you look into the wheel with for a given tire size.
My truck is a 1996 Dodge 2500 2WD. I went with Michelin Mud&Snow 245's about seven years ago. I think they cost me just under $400 each. I have had no issues with them at all. they do sing, or did, but I adapted to the singing. I definitely have a stiff ride with an empty truck. I got used to that as well.
The 19.5's will definitely reduce the sway due to heavier sidewalls.
Wayne