What if she’s about to change?

The agonizing part is that she says she's done work with her therapist, and by reading. She says she will be living with a different attitude, that she wants attachment, that "of course I want sex," and that I'd see that if only we were "trying" together.

I guess I've been hoping I'd see some signs from the outside: she'd talk about concrete things she's learned or read, she'd talk about things from her past she never talked about before, she'd talk about some of our past relational falterings and how she could now see how it must have been for me, or whatever. The only things I've observed are: she hung curtains and bought some throw rugs for the house, and she's said, a few times, "Before, I was afraid to feel feelings, good or bad, but now I'm not." Oh, and maybe three instances of reset behavior or whatever---throwing herself at me physically after conversations where she's way angry and says we're done. Gosh that makes things confusing.

So her offer and my dilemma: Commit, and suddenly you'll see a new me. And, I don't feel like I love you or want you right now, but if we were committed and "tried," as God intended, hopefully that would develop. For her, the right thing is to stay committed and trying, regardless of how she feels about it. For me, I don't get why this hasn't been "trying" all along. My door's been open; I haven't changed my phone number. We run across each other while trading kids multiple times per week.

Oh she's a master manipulator!  If you have the spine and can stomach the gall it would require, pitch the hardball back to her -
She may no longer be afraid to FEEL feelings but she is scared as the devil to talk about them and/or to make her behavior match what she is feeling.
"Of course she wants sex" sounds as hollow, to me, as hearing my mom tell me when I was young "you know your Dad & I love you" (no - I did NOT know that and saying it in words in between treating me like a nuisance is not very convincing either!)
Tell her you want to see her change, hear some "from the heart" discussion and then you may be willing to try but that you do not understand how the past X period has NOT been trying.  By you not retaining representation YET and initiating formal divorce proceedings, you have apparently been the only one still trying - what the hell has she thought you were still doing...hanging on because you're afraid to be alone?  (Oh - I guess that is HER tactic?)  Maybe I'm just projecting but she is fearful of losing something - namely her control over you.  IMO.
Sorry Ted - you're up against a fairly strong demon here.  She's may keep lobbing reset sex at you with a vengeance but I don't believe her heart and spirit are even related to her control tactics.
Good luck, man.

Or these days, a systemd timer.

Gosh, there really is a lot of good advice here. I deeply appreciate it, everyone. If I seem thick, it's probably that half of me agrees with you but there's a big, thick part of me I'm fighting with.

Wow, boulderbob, holy cow, this fits like a glove. (She never confided much in me, all of that's locked up deep inside where even she tries to pretend it doesn't exist. But I don't think that's a critical ingredient.) What a great set of resources, thank you. There's a lot to learn there.

I thought the rescuing was a part of love. I'm not sure what I actually did to try and "rescue" her. I don't think I ordered her around or anything. I tried to be there, available, kind, dependable. I did ask, though not too frequently, that she consider counseling, given her history and our problems. (But she mostly denied we had problems, at least problems that weren't my doing. I was the monster who just wanted sex all the time and nothing else---you all know that drill, I assume.)

I definitely enabled her to avoid her issues. Her MO really was to bury the past, and pretend problems didn't exist. Every morning she woke with no memory of the previous day, apparently. Like Dory. Nothing was ever resolved. And I had a choice---play along so as not to upset her, thereby having a chance at happiness, kindness, and maybe even affection that day; or stir up trouble and guarantee we'd be as distant as the US from Russia. Most times I chose to play along and hope. After all, it was closeness I was after, right? So, whatever it takes to get there must be the right thing, right? This is probably the #1 thing I've learned---with the help of counseling and friends---that I got wrong, badly wrong.

But yeah, the force is still strong within me. Telling healthy love apart from codependency, appeasing, rescuing, etc. remains very hard. I'm scared I'll never figure it out, and I'll just keep hurting myself over and over.

ted, some perhaps obvious / lame suggestions... Coffee talk. Date nights.

She should be able to have deep conversations with you about meaningful revelations from her therapy and studies, not just "commit and you'll see".

And, short of moving back in to experiment, dating her again would set the stage for her to start exhibiting some of the changes she claims, in a setting that's free of household activities and kids. (And ideally, a setting where she can't jump straight to sex in lieu of demonstrating any real changes.)

Those are my thoughts on how you might test the waters and see if any real change is to be had. Otherwise, it doesn't sound like she has much to lose by perpetuating your current arrangement. Being pessimistic, I'll observe that the alimony hole is being dug deeper with every year you let this arrangement continue.

ted, I think the fact that you are not just blindly accepting "self-sacrifice" or "rescuer" as the solution in your relationship dilemma means you are going in the right direction.  It is not only sex but her withholding intimacy that is very troubling.  Especially for the length of time it has gone on.  You must be certain that she proves that she understands the hell she put you through and will not resort to this tactic again.  

Ted, I felt that even though you may be in this category (caregiver/rescuer) that you are far from the only one on ILiASM, based on all I have read.  It took me years to figure out how to ask for what I wanted and not automatically give her what I knew would please her.  And that is okay to want to please, it is wonderful if two people try to please each other.(Physically, spiritually, emotionally, intellectually, etc.) 

Stay strong!