@kettlesquats,
You seem...rather self centered here. It could be my imagination but...um...you don't seem to think you could possibly be the issue.
Now don't get me wrong, she may have plenty of issues, but namely you're her biggest one. I'm not all that sure what this is supposed to mean, "She acted totally fine trading my money + back rubs for sex" because it reads like a prostitute that you gladly pay. In which case, she may want a pay increase.
And why does her family know about her lack of sexual prowess? EW. That's a really weird conversation to have - "Psst, mother-in-law, tell your daughter to have sex with me more often!" Leave her family out of YOUR marriage, that's helpful advise for anyone, let alone you.
The comparison of losing one's legs as a simile for your marriage is well below any type of "support" from a husband to his wife. That's not nice nor is it fair. Be careful of such comparisons, they do tend to come back to haunt you at the least opportune time.
If you think you're frustrated, I can only imagine what she feels, being married to you. Sex isn't a "job" to be performed like a dancing monkey so if you continue to treat her like one, you're be the one who's unemployed as a husband.
Rub one (or a few) out once in awhile, you're not helpful, just lazy.