Is it possible that my H is just using me for sex?

It's possible.

Is that something that men do?

Some men.

Should I continue to be open to him in this area? Is this a good thing that can bring us closer together - or is that just thinking about it like a woman?

Sexual intimacy can bond. Having said that, I can't say what's going on in your sitch. Should you continue to be available to him sexually? Rough call for someone else to make. Maybe the answer is in the asking of "Are you two in it for different reasons"?

So I'm thinking, that's great, he's thinking about me and at least future financial plans. That's good, right?

Don't know. I've read lots of posts written by LBSs that are shocked when the bomb drops, reporting that their WAS just spent the last week figuring out plans to put an addition on the house, booking their annual vacation, in other words, doing things for their future.

how can I be open to him but still be detached enough to not miss him and to not have such a strong desire to be with him? Every good interaction between us leaves me craving more.

I think desire comes from dwelling on the object of the desire. Maybe seeing 'good interaction' as sufficient in itself and not make wanting more of it a part of what happens next? Modify that behavior by relishing the interaction for what it is, and not for what it may portend or what you wish it would lead to. Like appetite control. Instead of eating apple pie and saying, "Mmmm, that was good, I'd like more!", learn to feel instead, "Mmmm, that was good!"

NY, I need a tongue lashing right about now

Is that one of them there sexual things you do with your H? I don't want to know about it!

The worst of it is, that the same advice I give others, I can't seem to practice myself

You're not emotionally attached to everyone else's WAS. I sometimes have to concentrate real hard in order to advise myself what I'd advise myself were I someone else. It's a bit more difficult to get through all the intimate entanglements of being so close to the sitch. But if you can think it through, so that you know what you need to positively do (in other words, it's not just a reaction or doing something based on how you feel but rather intelligent thought was given based on DB principles in accordance with your major plan), then the next step is that you'll convince yourself that [whatever] is the thing you must do, and just do it. The more you do that, the easier it gets, like anything else. Keep your eyes on the prize.