English, my DD started mucking around with her feeds at about 11w (ff too). She dropped down to only having about 25oz a day, which was almost 2 feeds less than the recommended amount for her size - she kept spitting the bottle out, hitting it away, getting very stressed and crying a lot when feeding, splitting her feeds so it was 2oz here, 2oz there. The drooling and hand chewing started then as well. I got really stressed about it, which didn't help as feed time became issues.
It turns out that there was absolutely nothing wrong. She just didn't want as much food as she had been having. About two weeks ago (so 16w) she started eating much more, suddenly added about 8-10oz onto her daily amount. I kept getting her weighed and pestering the HV's for advice but she was putting on weight so they all said she was fine. And she was
.
11w is about the right time for drooling and hand chewing to start naturally - I was sure it was teething but now she's calmed down a bit I can see that it wasn't really, or at the most it was a few teeth moving around high up. Hopefully your LO is just changing his habits and will pick up soon. Obviously get him checked out if you think he is a bit poorly though. I assume his nappies are still wet?
The two things which really helped us when DD was being a right pain mucking around was 1) offering food often, and not worrying about her usual timescales and 2) dreamfeeding through the day. We had one awful day when she took all her feeds as dreamfeeds! But if you have a bottle ready for when he wakes up he might feed more easily when he is a bit dozy and calm.
Hope it gets better soon, but I just wanted to reassure you that it sounds like something we went through that wasn't a serious problem at all in the end x