1. It seems correct to me.
2. Keep it like that until your strapping is done and then take a decision if you fear they could become too short. However, i would trim the ABS that flares up on the right/hand side and then even the opposite side.
3. The shoulder bridges are riveted on the chest plate and yes they'll need some heat bending. Boiling water is hot enough for this job normally. On the back, i really don't know how they're secured. You can see duct tape on a ref pic but i doubt this is the way they did it, maybe velcro or free floating?
However, i'm pretty sure ROTJ armors have no elastic shoulder bridges and that the chest/back plates rests on the wearer's shoulders directly via the ABS bridges. One way would be to use suspenders for the Ab section and the Kydney/butt plate, to prevent to put too much weight on the ABS bridges. You can see it done on the ESb MkII armor which is close to the ROTJ.
4. I really don't know for that but i'd drop few glue dots here an there just to be sure.