Hi J.! It's so great you're still nursing! What a wonderful gift you're giving your son, emotionally and immunologically!
I am still nursing a 26 month old, only on one side! ha ha Right around your son's age we experienced the same thing: distraction making it difficult to focus and nurse. It's my understanding that that difficulty reflects new curiosities and developments in your child, and doesn't mean they're ready to wean. So first off, I want to encourage you to persevere! A couple of things helped us, both of which really fell under the blanket idea of redefining our nursing relationship:
12 months is definitely late enough to refuse to nurse when he bites. Don't yell or jump or grimace if you can avoid it. Stay totally neutral. And remove him from your breast and plunk him down, not rough, but abruptly and with a firm, "NO BITING." You can try nursing again in 10 minutes or so. Just be consistent. It's most likely just an exploration of cause and effect.
Re: night weaning. I hear you. I was still up 6-8 times a night at 12 months. It was AWFUL. We finally night-weaned to a sippy cup 1/2 full of water, the ONLY time he got sippies. I gradually gave him less and less water. I'd rock him with the sippy if I had to, but he wound up not needed me at all to go back down, and it happened fairly quickly. Once he was down to a very small cup, I took away the sippy and let him have a tiny regular cup as part of his nighttime routine. Start by offering water once a night and increase from there. I bet he winds down on the night calories and ups his food calories on the dayside.
Re: distraction. Yeah. That just happens. Nursing a toddler becomes a whole different deal, things are more interesting than our boobs. Which honestly, they should be. Who really wants a toddler to be so boob-focused that they refuse the world's distractions to nurse? It doesn't mean wean, it means, "Wow, the world is really amazing! What's that? Did you hear that?" You know? :)
Make a ritual, that's fine. As PPs have said, it's not really about nutrition anymore. It's about immunity and emotional development. You don't have to be doing it all day. Your body will catch on and the engorgement issues should fade. You can move more towards a "Don't offer, don't refuse" stance. Make it a way to reconnect, to soothe, to transition, to quiet yourselves. When he doesn't need it, it's ok.
Hang in there! You're doing great momma.
~V.