DBT is alot more suitable than CBT, which is more applicable to simpler problems.
So from what I understand
OP was working and was studying (on a scholarship)
She earned much much less than her husband, but paid equally for bills/ life.
They had seperate accounts and he was earning enough (especially with bills being subsidised by OP) that he didnt really think about money at all, and could spend willy nilly on whatever he wantyed
Meanwhile OP was struggling to meet her 50%, and with everything coming out of her account, she also held responsibility if it was defaulted. I imagine that he paid his share, but maybe grudgingly(?) and questioning anything beyond a household bill
As her income was much less than his, and she wasnt paying p[roportionately, she was reliant on his good will or not for anything she needed, and that was not forthcoming.
OP says she still conrtributed while she has been out of work - at the moment from cash she has inherited, maybe previously from any small savings? People seem happy to jump on the fact that she isnt pulling her financia weight, but I would argue that she has been paying far more than her fair share, and living in an incompleted house for years on end (I seem to remember that in many ways its unsafe, with floorboiards up in some places) having her card refused in the past, while he is earning good money and the mortgage paid off, is hardly freeloading.
Leave OP.
Take the value from the marital house and half the savings, and get out. Live in Tuscanty. Live somewhere mortgage free. But get out. The good times are gone. They were only good times because you were bankrolling your future and getting free holidays. You are worth more.