andy, i don't know much to anything about mlc. my h had a crises due to too many transitions. a tlc.
it makes sense that your w came to the realization of your son's autism and the affect it would have on all your lives. she had to build some defense to adjust to her new reality. much like she said she didn't want to resent you so she was going to do what she needed to do and not feel guilty, well she must have had to do some of that with your son. perhaps her defenses are overdeveloped so that she doesn't allow too much feeling in. going out as couples is fun, but distracting in a way. an escape from a one on one intimate discussion. seems like your w is trying to keep everything surface calm so as not to feel too much of anything.
i may be totally off target, and i certainly am not as eloquant(SP?) or have had as much life experience as your other friends here.
she may miss the mf, because he provided a distraction without the resposibility of an intimate relationship. she probably is in withdrawal of some type and using family obligations as an excuse to not try to fill that time with couple time.
she will have to reach out to you at some point. she must be awfully lonely. her "cover" of independance is a protective shield. i wish i knew what to say that would be the magic answer. i think she may need time and therapy to let her defences down. we all have resentments. it's normal. we deal with them, discuss them. why is she so fearful of this emotion that she is shutting herself off?

i hope someday i can say something that helps you as much as you have helped me. lisa