Whatififly,
I think your strategy is working. With your MIL consider using a "problem" or two that you nor her can resolve. Then whenever she brings up church in conversation and climbs up on her high horse, all you ever have to do is pull out your problem card. You can preface your problem with the essays as your source and point back to LDS.org (as you did with your FIL).
Here's two examples:

Joseph married a mother and her daughter – Patty Bartlett Sessions and Sylvia Sessions Lyon.
Your confused because God said in Leviticus 20:14, “If a man take a wife and her mother, it is wickedness: they shall be burned with fire, both he and they; that there be no wickedness among you.” (Also see Lev. 18:17.)
Ask your MIL to help you reconcile this.

Joseph married several sets of sisters (Huntingtons, Partridges, Johnsons, Lawrences). Your confused because God said in Leviticus 18:18: “Neither shalt thou take a wife to her sister… to uncover her nakedness, beside the other in her lifetime” Leviticus 18:18.
Ask your MIL to help you reconcile this. If she starts to parrot the excuse that these women must have been widows or “old maids” and their prophet was doing a favor to them by marrying them point out the idea that Joseph Smith somehow rescued his plural wives from being single is just not accurate. The fact of the matter is that Smith met the majority of his wives when they were just preteens or teenagers. In fact, about a quarter of Smith’s eventual wives (nine of them) were 12 or younger when Smith met them, even as young as 5 (Sarah Ann Whitney) or 6 (Nancy Winchester). Over the years, Smith nurtured these relationships until he married them.
Finally, loop all of these issues back to the church essays as the source of your "problems". Ask them to help you reconcile with belief.
This strategy works really well with the temple too. If asked why you don't go, explain that you keep getting weird vibes whenever you do endowments and that you find the whole thing weird and disturbing. The solution offered to you will be to GO MORE! Then you can tell everyone you prayed about it and felt that God answered your prayers by telling you he was fine with your limited participation.
Mormons can't solve problems when the church is the problem. It just creates an infinite loop of Sunday school answers. After time they will just stop starting the loop thus leaving you alone!
“It always devolves to Pantaloons. Always.” ~ Fluffy
“I switched baristas” ~ Lady Gaga
“Those who do not move do not notice their chains.” ~Rosa Luxemburg