Welcome home PL! Seems so much has happened. I'm a bit scattered these days, and self absorbed with my own agony in a way I hate, but wanted to respond in some small way to your post.
First, I'm so glad and proud and uplifted to hear about your trip being so positive. I am scared to dip my toes in those waters of friends and family for fear I won't be able to fake it when necessary. It seems like you walked a tricky line - open with those who are supportive, and steady with those you are unsure of. Well done.
Now:
She told me that they have been married 15 years, and that it is not always easy, and that she feels much of the work of the marriage is up to her - that the wife must take on more than her share to maintain the marriage
My own mother is horrible at giving advice on anything useful, but my sister reminded me this weekend of one little jewel. She told her on her wedding night that people think healthy marriages are 50/50, but really they are more like 90/10. Now, don't worry. The 90 is supposed to change up - sometimes you carry the load, sometimes your partner does. We are well matched with people who are not necesarily exactly like us, which means we each are responsible for different things - even emotionally. This isn't a bad thing. Now, all us DBers here are carrying more tlike 99.9% right now, and will for a while, but this is a the worser, the poorer and the sickness we all talked about in our vows. Time to pony up. I don't know about your SIL's assertion that women always carry the burden (she might change her tune if she read up on GH, RB, Parob, MrMD and others here) but just wanted to add my mom's 2 cents after 38 years of marraige. BTW - good for you for not getting defensive when she said this. What great self-control. Aren't you glad she felt close enough to you to even bring it all up with you?

D also told him that OW is not planning to leave her H amd family, but that we want him in our family. And she capped it off by saying she loves him.

Isn't it wild how our relatives can talk openly when we can't? I finally told my sister about my sitch over Easter, and when H returned from seeing OW, there she was saying "I love you and want you to know there is room for you in our family." H told me how "nice" sister was to him. If I had said the same thing, he would have felt I was giving him a guilt trip. Now, it is possible that he still feels pressured by this - and that's why I'm bringing it up. If pressure from us is no good, then pressure from D is likely dangerous as well. Beware of thinking she is your secret agent. It might be worth letting H know she is talking on her own behalf, and is not your mouthpiece. (?)

It is tiring, draining, to be so thoughtful of every action I make, every thing I say, and to be so analytical of everything that is transpiring so that I can figure out what to do or say at that next short encounter. We have so little time together, and my life is moving. He is still giving the emotional attention that I want to another. I have concerns that I could come through for him emotionally (I would do everything in my power to achieve that) if we recommitted, but I'm not sure that he will come through for me even if he drops the OW. I am not sure that he will make the effort.
Yes, yes. Constant attention and analysis is too exhausting. I'm going to give you advice that I am working on taking myself: Let it go. Don't try to second guess his every step. Note the improvements for sure in your goals journal, but then move on. Focus on yourself. You can't know if he will return, if he will be able to offer you enough if he does, or even if this is worth saving right now. I trust, though, that you will know when you get there. Now, here's a bit of advice from a crsuty old soldier my husband used to work for: saw the wood in front of you or you never get through the pile. Honestly, its a luxury to be debating the terms of reconciliation, and we are not there yet. Saw the log in front of you.

I am wanting to have a R talk. I wanted to say at least, that I have a request - that if he has a complaint about me that he bring it to me, not others (such as OW or D). On the phone, H said he wanted this to be handled "between us", so I'd like him to create that instead of just expect it from me. Is that OK? I want him to share his feelings about me directly with me. Even his anger, his disappointment, his resignation.

Okay, this is the advice I am least sure of - but here goes: Don't. Don't try for an R talk in the name of honesty. I think you are falsely assured by D's successful talk with him that you too could have a heart to heart. I don't think you can. You are not his step daughter, you are his wife. And, trust me, I don't think you do want to hear what he thinks about how you "failed" the M, or pushed him to the A or any other silly crap these WAH's have told themselves to *rationalize* the A. When he decided he wants to recommit, you will identify the things that made him ripe for the A to happen, but right now his head is filled with lies, and I think it is best if they keep it to themselves. SO much of what they think now will just fade away if they come through the alien fog, and I think it would only hurt you and confuse you in the meantime. Also, in my experience, H is lying left and right anyway, so how could you trust anything he says?

Alright. Enough from me. I want you to know I admire how you are moving in such a stepwise fashion. I love your attitude. In the meantime, remember that it doesn't matter if H is warm toward you because of guilt or love or anything else. Just know that you will KNOW when he is sure he wants you. Until then, just keep taking care of yourself and remember your goal: to keep a safe space for your marriage. Indeed, it is a sacred place, even in the midst of all this.
erin