The first thing to do is to start putting him down for naps at regular times, and putting some space between feeds and sleep. At this age he can probably manage around 2-2hrs15mins awake between naps - that includes feeding, winding down, falling to sleep. So tomorrow morning you'd wake him, feed, then at about 1.75hrs after his feed you'll take him upstairs for a short wind-down. Keep it brief. Just a few steps so that (after you've repeated it 50 times) he knows it's going to be sleep time. So like, nappy change, close curtains, into sleeping bag, sing song, into cot.
Presumably he'll be crying up a storm before you put him in the cot. Lie him down anyway and spend a couple of minutes at least trying to settle him in his cot. Stroke his head, sing to him, stroke his back, jiggle his mattress - anything you can find that helps him to ease up or at least not escalate his crying. If it's not working, pick him up and hold him, pat his back or just cuddle him, tell him it's ok he's just going to sleep. If he starts to calm down, great, if not, lie him back down anyway and try again to settle him in his cot. Keep doing this for 45 mins. I expect he will skip his first nap. There will be a lot of crying but keep in mind he is not in pain and not afraid, just tired and frustrated because he doesn't know how to go to sleep without nursing.
So after 45 mins you bring him out of the bedroom and do a little bit of low-key A time. You might need to nurse him (depends what time it is by now) but don't let him fall asleep on the boob. Feed him in a well lit part of the house and as soon as he stops actively feeding, take him off the boob and keep him up for 5-10 mins before heading upstairs and going through your wind-down routine again. Try again to settle him for a nap just as described above. 45 mins. He might skip this nap too.
Keep going. He will fall asleep eventually, and the first time he falls asleep without nursing will be a breakthrough, because then you will both know that he can do it.
At bedtime, don't take a break after 45 mins, keep going until he sleeps.
Overnight, I would feed him at 10.30am. If he wakes up before then, settle him without feeding. (if he wakes up at 9.30, and it takes two hours, still settle him without feeding - you can feed him at his next waking). If he wakes and it has been less than 3-4 hours since his last feed, settle him without feeding.
It will be hard but you can do this. Keep his A times short - after a short nap he won't manage a full 2-2.25hrs awake, so cut it back if he has a short nap.
Before you begin though, are you sure he is not in discomfort?