I'm sorry it has come to this and hope he finds a better path soon.
I didn't let go of my son for over 10 years, and it almost killed me while he continued to use. It took me that long to realize and accept that "I am powerless over my son's addiction".
It helps me to say a prayer every morning and give his care to God. I can then live my life well, as life was intended to be lived.
His wife and son may need to explore alternative means of support. You can't count on an active addict to be responsible for family needs and commitments and the better prepared she is, the more options she will feel are available to her.
I will keep your son in my prayers, it's just sad to watch someone we love self-destruct.
Hugs