Hi Kate,
Wow, there is quiet a lot going on at the moment... all of which might be causing your LO to wake at night!
I guess how you approach it is up to you but if you're starting to see that he is unable to settle without being rocked or fed then it probably is becoming a prop. By 11 months, DD1 was sleeping straight through but DD2 still had 1 NF (I think she was completely done with night feeds by 12 months). I would say if he's taking a full feed and then settles for the rest of the night, he might be genuinely still needing that feed? Whereas if he was waking up a couple of times and just nibbling a little and then back to sleep, then that would probably be more of a prop issue? Also if he's at nursery, it could be that he isn't eating well enough there? So maybe keep the feed for now and continue to slowly work on weaning it by diluting it. If he's sick at the moment, it could be that he's not feeding well during the day and making up for it at night?
With regards to the rocking, I would probably stop rocking to sleep... although this is hard because he might be needing the extra cuddles since starting nursery. Try to do a longer windown with lots of cuddles and one on one time with him before you put him down for the night and if he wakes at night, try to resettle him by maybe rubbing his back to see if that will help settle him (this method always worked best for my girls) or you could do pu/pd but I would be careful with the rocking personally as it can quickly become a prop issue...
With regards to teething... I know everyone does things differently but personally I didn't really medicate all that much for teething and I think I only ever used it with DD1, when she was teething her canine teeth and I only did it a handful of times and only gave baby panadol. I've read somewhere that teething meds (i think its more to do with ibuprofen and teething gels) can have the opposite effect and actually keep them up instead of helping... so that kinda freaked me out LOL and plus they will be teething for a long time and I didn't think it was necessary to medicate before every nap and bedtime. But if he is uncomfortable and you think meds are helping, then of course you can give him to rule it out.
I also wonder how he is going down at nursery? Do they follow the same routine as you.. could it be they are helping him go to sleep and he's expecting the same when he wakes? It might also be that they are letting him sleep "too long" - as in, the morning nap, where he could be making up for the lost sleep at night, which in turn can cause the wake ups at night (its a bit of a vicious circle)
With regards to him feeling unwell - do you have a vapouriser you could put on before he goes to sleep? Or perhaps elevate the mattress? You could maybe try and ride it out until he's at least feeling better (cold/runny nose) and then use the pu/pd method to sleep train.
What do you think?