You might want to read a thread called
"Remineralization and diet for healthy teeth".
I found it by typing in "diet" in the search window.
Also another one is
"Told to Wean/dentist/Mom's opinion and BF/Dental Caries"".
I believe the white spots indicate the decalcification of the teeth which leads to decay.
Is it bm in the bottle or?.....regardless....
It certainly would be better to either brush his teeth AFTER the bottle or at least wipe his teeth if brushing would upset the calm....or...
if it would work, give him the milk before brushing and then put water in the bottle for the "rocker time."
If it is indeed bm in the bottle, then you will find plenty of support for continuing. As Smilemomma says, "weaning is not the answer to dental problems"
There is a lot in those archives, so if you need some help finding specifics, I might be able to point you in the direction. I just recently read a massive amount in dealing with my dd's dental problems. The two that I suggested are a good place to start.
So in answer to your last question....
Worried, no.....concerned, yes! (which of course you already are
I believe if it is just white spots at this point then you can turn it around meaning that you can remineralize the teeth. If you haven't been to a dentist yet, you might want to think about making an appt. to see what's all going on......(any possible decay that is not obvious, and advice on those white spots, etc.)