So many hugs. I know this [censored] to h*ll and back.
If you are in NYC, things are so expensive. But you probably should talk to a couple of other lawyers, just to compare costs and points of view. Around here, many attorneys will do a free initial short meeting.
(If he had consulted an attorney on his own, he would know that there is language that is common in decrees that spousal support ends if the receiver remarries or co-habitates with a romantic partner. (don't want a roommate situation to end SS)
When I was meeting wit attorneys with a friend, at least two of them said that the leaver always thinks divorce is easier than it is in reality. Often, they haven't really given things a thought more than actually leaving. They are surprised that the reality is what it is.
Did the mediator provide insight to him or you on how things really work?
Do you think he has a clue that you might fight back? When he said file for temporary spousal support -- did he think you would do that on your own or get an attorney?