It's ok I think to have a quick morning CN to get you through to proper nap time when you are trying to push the day on (if he's still willing/able to take two naps). If you get another 4.30 morning for example I might have done a quick 15-20 mins around 9am to get through to a later nap at 11.30/12 and help push your day onwards. But only as a one-off, not as a regular thing at this age. Just for comparison our day usually looks like WU 6.30ish, nap 11.45/12 for 1.5-2.5h, BT 7.
It's up to you about the bottle really. If you want to push the day forward first then go for it with the bottle then by all means do. I wouldn't wait for the 'perfect' time though - at this age there will always be teeth, colds, developmental leaps etc etc - you could wait forever and never get on with it if you see what I mean. I'd go ahead when you are ready, even if teething. You aren't starving him, I'm presuming he has ample opportunity to eat and drink during the day? If he's hungry but only wanting milk because his teeth hurt, give the milk in the daytime. The fact he has milk overnight may in fact be fuelling the not eating so well in the day - if the night time calorie opportunities go away he may well eat ok even if teething.
Hugs, I know how tired you must be after 18 months of this. But keep going, we are all here cheerleading and wishing you a good nights sleep xx