i dont really consider myself experienced enough with the program to try to structure your program but heres what i'll say:
for your first cycle of 5/3/1 go light on the assistance work. the program is based on the main lift and the assistance work is there to help assist those lifts and for a little extra work so start easy and gradually build up as the cycles go on so you can get a feel for how much volume your body needs and how much you can do without affecting the progression of your main lifts.
also are you lifting 3 or 4x a week?
and whats the reasoning behind doing DB Shoulder Press instead of standing barbell press? i'd definitely recommend using standing barbell press for your main lift. you can use DB presses for assistance if you'd like.
the more experienced guys will be able to help you more but good luck! i'll be following your log for sure