Dog, I know I'm coming in late here, but have to address her statement that no one else would put up with your ex wife or love your children like she does.
This is not what the vows said, were they? Granted you have an exwife, and kids-- they are part of the package. But she promised to love and honor and forgive (or something) YOU.
This a a diversionary tactic, and one you should call her on. Most men your age have an ex-- so women who are interested in men your age know they will deal with an ex. Children are by nature lovable, even the ones who act like monsters on occasion. I'd take offense at her having a low estimate for people in general being able to treat your children lovingly.
Even if your ex is a shrew, and your kids can be difficult, there are many women who would feel quite fortified for those challenges by regular, good sex. (speaking for myself, my tolerance for life's quirks is almost infinite when I am sexually satisfied.)
I'd say, DO NOT let her divert your attention from the core issue. You are talking about a huge void in a marital relationship, not her diplomacy skills with ex wife, or her step parenting approach.
