My H and I are also in our early 40's and it can be a difficult stage...there are all the past issues of a long standing marriage coupled with the realities of life ( aging, finances, kids, etc). I hope your H is able to see the destructiveness of his fantasy quick-fix solution; until you are confident he is heading in the right direction, you need to protect yourself financially and emotionally. While it is generous of you to try to meet his needs, he has to be willing to show a commitment to you by understanding what you need to be happy. It goes both ways. Trust your feelings; it's one thing to go along with "spicier" kinds of sex...it's another to participate in anything that makes you feel uncomfortable or bad about yourself. You have to draw that line. Take good care of yourself...are you ( or H ) in counseling?
