a Big No....
You have tolerated a major portion of life in such pain ,it is better to hold on. Don't quit your job that would make you lame, concentrate on you job. Your son is still not in a position that he will give you the caring suppourt as requiered.
You daughter's marraige is your priortym try to invest you mind and energy in that development, ignore what affairs your husband is having as he will not turn to be so as expected by you in few days. Talk with your husband seriously about the marriage of your daughter, and suppourt your son till he is gets settled, just little more time and your worries will end. There is always light at the end of tunnel.
reagrding seeking maintenance through any legal way is not good at this stage, if you quit job ( which you should not) then your husband is bound to maintain you .
However to marry your daughter is the duty of your hsband you should compel him to arrange for that.
Divorce at this stgae will spoil the situation and will add any good for now.