All my kids have worn amber too.
My first two also had symptoms like you described and my ILs were adamant it was 'teeth'. Some BF babies do have runny explosive random poos. Some kids just drool - a lot. Fist chewing is also developmental - but it can also be a sign of an ear infection
DD1 got her first tooth at 10months, and at 11 months got 11 teeth in a fortnight. When it did happen I didn't even notice lol.

Sorry that was a ramble for - it could very well be his teeth. But it could not too. Oldies seem to want a reason for everything, but sometimes there is no reason with babies. If you're worried, perhaps a chat with your MCHN? Otherwise, sounds like you're doing everything you can.