That is great news indeed, I'm so happy that she has taken such a big step. A few thoughts from the last few weeks...
-- when your W complains that you abandoned her far too often to take care of the kids herself, you seem to hear that she wanted you to take care of her and "fix" her. I hear that she wanted to continue to have a life outside of being a mother but that you kept her from that by being inconsiderate of her time. That is, she wanted space to be an adult and have friends and other interests, she did not want you to fix her or coddle her.
-- I recommend ignoring this point. For some reason I feel compelled to say it, lol, but it probably isn't very useful for anyone. My guess is that you'll get sex pretty close to six months after she was last with OM, which is the period they tell you these days is pretty safe in terms of STDs.
--Don't let your W dump on you, call her on it. For example, she seems to have been whining a bit about how she can't talk to you. (1) She can talk to you and is hurting you both and your R by withholding that kind of intimacy. (2) Whatever "happened" on Sunday which she did not tell you about is the real problem that is causing her distress and is likely a result of her own actions, again it is not your fault.
--Stop cleaning up your W's life messes caused by her drinking. She needs to clean up after herself.
--Maybe time for some directness -- "W, I feel scared and insecure when you tell me there are things you can't tell me about. Part of this is because of the A, part of this is because I fear roadblocks to real emotional intimacy between the two of us. I'd really like you to trust me enough to share with me what happened on Sunday."
--It seems like W is really beginning to make some real shifts in her own life, and shifts that are in a positive direction :-) This is really wonderful news and I expect your R will reap the benefits.
Best, Oldtimer
P.S. I probably won't have time to write back, but I do always check on you :-) I, Newtimer, and Mr. Oldtimer are all doing wonderfully :-)