I hear that it is painful and causing a lot of heartache (you, your wife) despite you trying to help mom so many times. It is very unfortunate that mom is blind with regards to her son. But yes, sometimes the least painful thing to do is to disengage.

There is only so much one can do for another (i.e. mom playing helpless so you will help her and even Jeff is benefitting from that help) at the detriment of ourselves..