This reply is all about you, chief. Hang in there.
I agree with another poster – try to do things to get out of your own head as best you can. This is a stressful situation, so that’s easier said. Exercising is great advice, but it may also help to try meditation or breathing exercises throughout the day, especially when you start catastrophizing.
I totally understand you miss the physical intimacy of your relationship, anyone would. I bet she does too. If you’re not pressuring her for it and both of you are focusing on being a friend to each other again, it may come back sooner than you think. You’re hurt and she’s hurt, so if you did have sex right now, it might not be all that great or could end in a fight.
It sounds like you have compassion for her, but be kind to yourself, too. You have a lot of remorse over the past, which is healthy, but try to forgive yourself and learn from it. You owe it to your future self. Trying to work through things in your relationship without dealing with your own stuff is like mixing ice cream and manure. It won’t hurt the manure, but it’s going to ruin the ice cream. Do you have other people in your life who build you up or bring out your best? See if they’re available for coffee or something like that. Maybe focus on one action per day that lifts your self-esteem. Beating yourself up does no good and contributes to a crappy atmosphere in your home. Imagine: instead of coming home to you moping, your wife comes home to a warm, genuine smile and a “hi, how was your day?” Day after day after day. I’d think that would have a positive effect on both of you. Since you have ADHD, you’ve likely felt bad about yourself for different things all your life, and you’re probably pretty good at it. Try to stop that negative talk.
Her saying she needs time makes sense, but personally speaking, I always think someone saying that they need space is kind of nebulous. If you’re unsure about how to give her what she needs, I would consider asking her what giving her space looks like in a practical way. That could be a good topic in your marriage counseling as it’s usually a place to unpack things with the help of an unbiased observer.
Other than that, I would clean, pick up after yourself, do laundry, get up a little earlier and make the coffee, basically be a reliable partner on a day-to-day basis.
This is a crappy situation, but you’re taking action. Considering the fact that had you done nothing that your marriage would have ended, the way I see it is that you’re playing with house money as that’s still the worst thing that could happen. If things improve, awesome. If they don’t, you’re going to be okay and so will she. Really. I’m not trying to be flippant, just honest.
I would try to go boldly into this. The cave you fear to enter holds the treasure that you seek.