I wonder if he might be a bit ot - there is a growth spurt at 18 months which can lead to them needing more sleep. How long has he been on 1 nap? Mine only went to one nap at about 17 months, so at this age still very occasionally needed it to catch up - would he sleep for say 15 minutes at 10/10.30 and then have a slightly shorter nap at 1ish (like 1h45-2h) to help him through? The teething could also be making him more tired, so extra sleep is unlikely to do him any harm. If he won't do 2 naps, can you have him in bed earlier, like 6.15/6.30?
As for the bottle in the middle of the night, I would have thought that it wouldn't be too difficult to get rid of as it hasn't been a prop for long. Try giving him a bottle of water instead, as it won't be worth waking up for.