Good to hear from you. Just wanted to say that I have experienced something very similar with my mlc-er - I'm embarrassed to refer to him as my X now.
He has changed into someone I could never have imagined - the opposite of the man I thought I had a relationship with.
I have 2 kids from the years I spent with him, but apart from that, I would be feeling like you - that it was a sham and a waste of my time.
From what i can gather, this man has now broken up with the OW he left us for (after 4 years) and is now living back with his parent (at age 45) as he has no ability to live an adult life that involves budgeting for things like rent, food, taxes, etc. for himself. He continues to live a narcissistic life of indulgence and luxury on the back of someone else's income.
Just amazing, and humiliating to think I was so taken in by him.