Ah you're very lucky! Dh used to do my whole body too but these days its lucky to be a quick shoulder or foot rub. Actually he has done my b.oobs when I've had mastitis. Lol. Will he let you do other parts of him that aren't his back?
Ds doesn't bite much when feeding these days. When he was younger I would put him down/stop feeding him for a couple of minutes. Other times he would bite because he was "finished" on that side so it was my cue to offer the other side (I didn't always offer both as I block fed).