The only issue I see is the stoop. If it is staying (not being torn out) the proper way to frame around it is:
Double up the joists on either side
Hang a double header off them just outside the stoop
Rip 2× joist to clear stoop (sounds like these are only going to be about 4.5" to 5" joists. I'd probably add extra over the stoop, like 12" centers)
Ledger over stoop will need to be ripped down also