I think there's another theory, far less complex, that would explain her behavior:
She loves me, loves being married and loves our family, knows sex is very important to me (primary LL), but just isn't attracted to me.
In fact, by her silence to me asking her that last year, she more or less admitted that.
I think there's another possibility--what she couldn't express is that she's not attracted to "the It," or to you as a morally superior father figure. That's not supposed to be a slam in any way--I just think it's the way she relates to you most of the time. I wonder if, when there's a threat of divorce, you become less "fatherly" or less morally superior; or she's more in touch with her feelings of attraction to you because her barriers are down. Just thinking out loud.
M60 H52 D20 M14 yrs OW-old gf from 1986 bomb-5/18/08 H filed for D-9/10/08 D final 4/24/09 xH remarried (not OW) 2012