What I'm dealing with right now is the little voice in my brain telling me I'm being selfish for wanting this, and mean to him for doing it. My h deals with jealously a lot... .as in being jealous of me for doing things he doesn't have the balls to do... .and I am already anticipating this reaction, "You're just doing this for yourself and you don't care about me."
First off... .your husband is mentally disordered, and has very poor emotional regulation / emotional intelligence. (Yes, that is an understatement). So as a consequence, if he tells you something like "You are being selfish", be VERY skeptical about what he says. Don't challenge him verbally--that is invalidating, and you know that.
But don't believe him either--ask yourself if it is completely true, completely false, or someplace inbetween.
In addition... .I italicized two statements you expect to hear from your husband. Both of those are statements about what you are thinking or feeling, or what your motivations are. He's not a mind reader. If those thoughts exist in your head and are motivating you, they are YOUR thoughts, not HIS thoughts. My recommendation is to NEVER believe anything like this from him. [Aside: this kind of thing from my wife was triggering and pissed me off royally. I implemented firm boundaries that I would not participate in conversations where I was told what I was thinking or feeling.]
May I ask... .were you criticized for being selfish a lot as a kid? Especially in cases where the person accusing you was trying to control you, which is what this sounds like to me.
And I think he's suspicious of me right now. When I got up this morning, my new phone had been gone through. I don't have any lock on it or anything, and I've been pretty relaxed about letting him look at what he wants on it. But I'm getting the impression he is nervous that I've got some beau lined up to run off with this summer. I have nothing to hide, so I'm thinking being open is the best way to deal with his suspicions.
I'm going to disagree with you about this... .with the caveat that choosing your battles is a good idea, and that giving in on this one, and standing firm on the place to stay this summer sounds good to me... .but here's my take:
He's suspicious mostly because of his own self-doubt and self-hatred. He probably doesn't believe at his core that he is lovable, or that anybody would want to be with him. This leads him to 'natural conclusions' ... .If you say you love him, you are lying ('cuz he's not lovable)... .You only stick around 'cuz you aren't strong enough to get away, or haven't met other guys to cheat on him with... .You would jump at the chance to get away, and he's got to stop you / manipulate you / control you to keep you. etc. etc. etc. Most likely he isn't even aware of this stuff going on (!)
Anyhow... .given that... .being open won't fill that void inside him, so it won't protect you from his dysregulation or jealousy.
To make things worse... .from his world-view, where those things I mentioned are unquestioned facts, he could easily find something on your phone... .and twist it to match... .and use it as a trigger to blow up at you.
Related impertinent question: I've seen you sign off several topics with "Gotta go" where it sounded like you had things to type you hadn't got 'round to yet. Here is the conclusion I've jumped to... .Do you find yourself having trouble getting some time with enough privacy to post here? Are you afraid of him seeing you spending time on a computer typing something that is private and not his business and getting caught doing it, and facing a dysregulation / rage over it?
I think the change has come about because he now recognizes that I am in control of my body and what I do with it, and he has no say. My body, my choices. Take it or leave it. It's worked for me. The sex is much better (still not fabulous, his hang ups will always be there, but much more satisfying than in the past).

Having boundaries like that is fantastic.
The part I like the best is that once you realized that you had boundaries and could protect yourself... .you found space to be a lot more giving and generous than you had been. I'm very glad to hear that things are going better.
I'm having a hard time with all this, right now. I don't want to be selfish. I don't want to put him through undue pain. Because he is on his best behaviour right now, he is attempting to set the stage to say, 'there's no reason to leave, we are great together, and you are just being a b___ for doing this.' ... .wait a minute... .isn't this him manipulating me?
I have no doubt he is trying to manipulate you. I strongly recommend you enforce boundaries and refuse to allow this to work. That doesn't justify you trying to manipulate him. There is too much truth in this joke... .
Don't let them drag you down to their level in a fight. They will fight you there... .then beat you with experience!

As for whether you are being manipulative or not... .YOU KNOW. Trust yourself and believe in yourself. (FYI, one technique he might use to manipulate you is accusing you of manipulating him. Don't take such things from him at face value )
I cautioned you about it originally because your motivation wasn't clear from a sentence or two in your prior post. You could take the same action for a variety of reasons... .and while the action would be the same, I would call it healthy in some cases and unhealthy in others... .if that makes any sense to you.
Funny you should mention that, son and I were teaching him to text last night. He drew pics with the different symbols... .started with a simple smiley face, then a zombie cat, then a lady's body. Son commented that he was learning quick, he responded with, "I've got an ulterior motive." Then he bounced his eyebrows up and down when he looked at me... .you men, ya'all think alike! It would certainly be a new experience, for both of us.

Have fun with this one--Google how to sext / flirt over text with a guy... .when you have quiet time in your apartment by the water some evening. Plot and scheme what you can do which will excite and turn him on at that distance... .make the best of it!
You could even be subversive about it... .let on how excited and happy you would be if he did some other things for you... .in as positive way as you can. (The backrubs sound great... .perhaps you can come up with a way to increase the range of offerings that make you feel loved and aroused he has to choose from.)
This kind of stuff I'm suggesting here... .there is a very subtle line between being manipulative... .and presenting choices or options for him in a way that he can be receptive to them. Trust yourself to find that line and stay on the right side of it. If you notice you had a misstep and half your left foot came down on the wrong side of the line, learn from it, and do better next time.