What is the ruling on delaying the fulfillment of a vow to fast on Mondays and Thursdays for life, and what must be done regarding the past 16 years during which the vow was not observed? Is expiation permissible for it, given the effort and exhaustion caused by fasting, and the difficult family circumstances?

As long as you are inclined to believe that you vowed to fast for life, then you must fulfill it, because whoever vows obedience to Allah must fulfill it. Your delay in fulfilling it without an excuse is a sin, and you must repent. You are not required to offer expiation; the former is not obligatory. You must make up for all the time you did not fast, and fulfill the vow in the future as long as you are able, for exhaustion is not an excuse to be absolved from it. Making vows is disliked. If the ill-treatment is from the husband, then he should be advised, and his harm should be patiently endured, and prayers should be made for him.