The Quetiapine (Seroquel) is capable of altering blood sugar and raising it. I'd get that checked out ASAP.

I would also get the actual test result from the B12 test. Doctors are still using the old outdated lab ranges, and his "ok" may in fact be low.

Once people who were heavy drinkers, stop, and restore nutrition, any PN present typically can resolve. Benfotiamine (or regular thiamine) may also be helpful for him.

http://neurotalk.psychcentral.com/post653193-4.html

It is possible that all the sedative medications he is taking, are producing a "sedated, or depressed" constellation of side effects. Please keep that in mind.