Breaks my heart reading posts like this. My advice would be little steps. What can you do today (tomorrow) to help yourself. I was you all of last year. This is why I'm saying what I'm going to say.
How logical is it to move back? Would staying with family there (if there's space) for a week or two be feasible? Just to get some mental headspace in a place you're missing. Could also be used as an opportunity to see if there's any places to move to if DH agrees...
I'd personally forget about your DH being a knight in shining armour, doesn't mean he's a shitty person, some people just don't say anything when they don't know what to say. Speak to him again when you feel up to it, break it down to him how much you've changed etc and what you need. It might take him a while to fully digest it, some people get stuck in their ways, their own routines. Either way, nothing is going to happen immediately so this is where the other stuff comes in to it....
So far, you've only fed your mind negative energy. Not intentionally but clearly you're in a bad mental loop. Take some time to sit, find a mindfulness meditation video on YouTube and have a minute, it doesn't take long, just one minute to speak to yourself with some positivity. Imagine how you'd feel if you got the things you want/remember how you felt when things were great for you. Put yourself into that moment. Even if you were in a long lost dark, dingy jail somewhere, the power of imagination is massive. You need to be in survival mode now, you need to be your own hero. Let your mind and body soak in the positive energy. That's all you need to do. Just give yourself a minute daily to break the cycle of misery. No matter how silly you might feel.
If you ever did commit suicide, you will never get the opportunity to 'live' again. Imagine how much can change in one month/one year. You matter, your life is precious, please do not give up on it for a temporary page in your life. There is so much more to it than your daily lifestyle.
Not sure on your health issues, would yoga help? If it's mental, yoga can also take you away from the real world for twenty minutes. When my insomnia was bad, in my yoga class, we'd lie with a weighted eye mask on at the end and I slept every single time 🙈 the yoga helped to relax my body and distract my mind. Perhaps try a weighted eye mask and a meditation podcast thing with earphones in when you wake up through night? The lack of sleep will definitely be having a massive negative impact on you. Atleast it did with me. If your health issues are physical, speak to the doctor and see what can be done. I find (yoga again also, sorry to bang on about the benefits of it) making myself a green tea in the morning and focusing on what I need in that moment helps calibrate myself for the day. Taking vitamins and making smoothies etc, the placebo effect made me feel instantly better.
Sorry for the long post, you asked what can you do. Well, you do you. You spend time healing for the moment. You plan what you can do today to make yourself a little happier. You plan for the future but make now important too. You fix your sleep routine. Try different methods that help you to not instantly think negatively as soon as your eyes open. Love for today and plan for tomorrow, as corny as that sounds. You deserve to live a good life. You are the one who can save yourself. From one who was suicidal and day dreaming constantly of getting on a train and disappearing, I'm speaking to you from the heart, look after yourself. It gets better when we make decide to make it better ❤️