So you’ve been sitting on the fence for a long time and I think you need to decide what side you’re on. If you’re at the point where you’re gonna be friendly with him, ask for favors and ask him how his day was then you should respond to his text. If you don’t it makes you look like your pouting because he didn’t help.
Now if you choose the other side of the fence that he is in an open affair while still married to you and that you will not allow someone in your life that treats you that way. Then don’t respond.
Neither gets him back but one will earn his respect.
You absolutely positively can’t nice him back.
Relationships are about value and how you let people treat you. People will never do or say to you won’t you don’t allow them to. Do you know your value?