What should I do? Which technique to use?

[AnotherStander]

Me: I don't understand what you want from me. You want to feel welcome and comfortable and when I do those things and try to be positive about our relationship this is the result.

Poor response. Here's what you should have replied:

"Understood, take as much time as you need. I need to think things over too."

You continue to do things that totally fly in the face of DB'ing. You're supposed to validate her emotions and support her decisions even if you don't agree with them. Arguing is just the same old behavior that landed you in this sitch to begin with.

Me: What I said and did last week was stupid and I never really wanted to end it. Even if you don't see us as bf/gf there's still a relationship between us. I understand you don't have an answer but I also can't continually support somebody who isn't more committed.

Again, this response is nothing but arguing. Ask yourself, is your arguing with her convincing her of your position? Is it changing her mind? Is it improving your sitch? If the answer is no, no and no, then quit doing it!

Just remember that I'm still here for you, still doing all I can for you, that after everything that's happened it's still you, and nobody else, that I want.

Good grief!! Do you EVER look at the DB 180 tips? We've told you several times to print them out and review them every day if not several times a day. I want you to re-read what you wrote above, then read the below tips and tell me if you're being consistent with DB'ing:

1. Do not pursue, reason, chase, beg, plead or implore.
12. Act as if you are moving on with your life.
13. Be cheerful, strong, outgoing and attractive.
14. Don't sit around waiting on your spouse - get busy, do things, go to church, go out with friends, etc.
17. You need to make your partner think that you have had an awakening and, as far as you are concerned, you are going to move on with your life, with or without your spouse.
21. Never lose your cool.
23. Do not argue about how she feels (it only makes their feelings stronger).
26. Learn to back off, shut up and walk away when you want to speak out.

I ended up texting her that honestly I feel used and taken advantage of.

That is the absolute opposite of detachment. DO NOT text her!! DO NOT grovel!!

I don't understand how "Act As If" backfired so badly.

Because you didn't act "as if". Acting "as if" is showing her that you accept things as they are and that you will be fine whether she goes or stays. It's showing contentment and personal peace. I've read your whole thread and what comes through loud and clear is you've constantly done the opposite of acting "as if".

I mean, giving benefit of the doubt that's she's really not just out to use me, what do I do? How do I keep up helpful caring 180's and detach LRT style?

LRT is not detaching. LRT is what you do when all else has failed, it's for you, not her. It's to help you move on. One thing that is clear in your posts here is you're not even sure you want to save this R. That's the very first thing you need to resolve. If you don't want to save it, then by all means move on. Frankly that may be for the best for you, her and her kids. If you want to save things then you've got to make some kind of effort to learn the DB basics and live them and quit being so inconsistent in your actions.