I THINK I STATED ITS NOT ABOUT THE SEX!! To quote him "I';m old, I never want sex!
Yet, you also said this:
It is possible to make someone happy so they won't cheat or be unhappy with their partner! You just have to be able to satisfy a man, as cheesy as it sounds, with variety, and keep the excitment going, then he has no reason to want to stray. She is clearly not giving him happiness,
You think you can keep him happy with sex even though your relationship isn't about sex. Also something to consider - men in their 30's don't usually completely lack a sex drive & most would still like to do it several times/wk if not nightly. If he rarely wants sex this early in your relationship, then that is likely a sign of either a physical problem or an emotional problem.