OP:
I would agree to not going into 5/3/1 after SS. I did this and wasted close to a year. I got somewhat stronger in the main lifts, brought up weak points (upper back), and was able to lose some fat through dieting. All in all, not worth it.
Look into madcow 5x5, I am doing that now and should have been doing it all along. It uses ramping sets like 5/3/1 but without AMRAP sets (AMRAP squats/DL have nearly gotten me hurt and the form gets pretty ugly). The workload is spread out across the week which I think is a positive over texas method. Lastly, I switched Press and Bench so I press 2x/week and light bench 1x/week (sets of 8 - benching heavy irritates my shoulders).
The belt is ultimately a personal decision. After lifting with a belt for several months and then removing the belt and working back up over several months I have come to the following conclusion: I use a belt for work sets of squats and presses because I do not want my low back to limit my leg, hip, shoulder, and arm development. I do not use it for DLs or any pulls because these lifts are supposed to strengthen the low back so I don't want to make them easier on my low back. I do not compete in PL so my numbers were not guiding my decision. I found this to be the best compromise.