Hi there!
It could well be a combination of OT/teething etc & unfortunately you'll never know for definite
! I guess it's all about trying to come up with the likely problem then doing a bit of damage limitation....
OT cycles are when OT builds up over a few days (due to short naps, NW's, EW's etc), so the LO never really gets proper restorative sleep iyswim? To try & get out the cycle I usually try & get longer naps during the day (or try & fit in more naps if they are short) plus I do an early BT (which actually can help with EW's & even if it doesn't at least they have had more total hours sleep.
You mention about it being cold (same here too!), do you think that could be contributing to the NW's? Do you use a baby sleeping bag?
His food intake seems fine though you probably could drop to 3 BF's, especially if he's starting to loose interest, this should make him more hungry for solids & take more at the other BF's. Also, I've found that teething can affect food intake.
I think you are totally doing the right thing not rushing into him, a lot of their moans are them trying to re-settle & if you went in at that point they would lose their ability to do it, so going in when he starts to get distressed is right. I always try to re-settle in the cot first. You are not letting him CIO if you are there with him, he can see you & know your there for him.
I agree to use meds when you can see him suffering but maybe try some teething gel &/or teething salts when he wakes rather than Calpol (unless you feel it's necessary)?
Hope I've answered your Q's a bit?