Hi Jen and welcome to SR.
Here's what I would do in your situation. Your husband is young to be having dementia though it is possible (would be extremely rare). He could also possibly be a long candidate of alzheimer's (which would also be extremely rare, but possible).
Or there is a more plausible explanation....your husband has been misdiagnosed and is being treated with improper medication. I'm sorry to say its common. Because his anti-depressants which have been switched, are not working, is a VERY BIG RED FLAG. My guess is you might be dealing with bi-polar issues that don't play well with SSRI anti depressant meds. I am no Doctor, so that's only a guess. His memory issues and so forth could be a result of improper medication. Please do not discontinue those meds though, that needs to addressed by a professional and are not medications that one stops cold turkey.
If it were me I would find the best Neuro-Psychiatrist (both neurologist and psychiatrist) you can find and get him there Stat. This medical team is not helping your husband or you, they have come to a conclusion and are now blaming his actions on marital discord which is laughable. I'd cut them loose.
I'm sorry for what you are experiencing. I do not believe this is about the alcohol as his state is diminishing in sobriety.