Thank you babdoc that was a nice message and I appreciate your support.
I 100% know that when I'm out of this house my mood will start to lift. If I could draw a picture of what my mood is like then I'd draw me lying in the foetal position, that's how I feel most of the time.
In terms of the situation in this house, unfortunately my DH is not the type of person who would agree to that type of compromise. If I suggested we take turns of the garden he'd definitely refuse. I can actually envision how the conversation would go....he'd basically tell me he doesn't care if I'm in the garden with him, and if I care then it's my problem. Not his.
I really just feel too uncomfortable to be around him. Which is probably silly as I should be utilising my garden, especially when so many people don't have one. He's not good at compromise at all. When we separated at Xmas one of the conditions of me giving things another go was for him to look in to counselling, as I could see he was struggling under the pressure of life. I was throwing all my time and effort at my DD to support her but it was bloody difficult. His response was "if I need counselling to help me deal with family issues, then I shouldn't be in this family". I asked, begged and pleaded for him to consider it but he refused. Said exercise is his therapy. Stupidly I let my heart rule my head and gave things another go.
He's always enjoyed a drink, especially at weekends. I rarely drink now. His alcohol intake was steadily increasing over the last couple of years but more so in the last year, and even more so since lockdown. I've asked him repeatedly to cut back but I'm just met with refusal. He says there's nothing wrong with drinking alcohol, most people do it, most people have drank more in lockdown and if he wants to he will, as he's an adult. For a couple of weeks I started counting how many units he was drinking. One week it was almost 60 units and the next week it was around 90 units. In this time he was also hiding alcohol but I found it. He also drank an old bottle of mulled wine left over from Xmas, and my 2 fruit ciders (which he apparently hates). He still refuses to see he has a problem.
In terms of helping lighten the load with my DD. She is his SD and over the last few years they've had a very rocky relationship, and he's taken massive steps back. If he's annoyed at me about something then he'll use her as a way of getting at me. When I was previously working until 7pm (from home) he refused to make dinner for her. He'd cooked himself a Sunday roast, put on enough for himself and refused to cook for her, said she had to wait until I was finished work. That was the breaking point for me asking to change my hours.
I do know I need to try get out more and get back to my daily walks, I need to dig very deep to be able to get to that stage and I hope I can manage that soon.
DD is under the care of a dietician, ED (eating disorder) family therapist, MH nurse and psychiatrist. She is on the waiting list for a psychologist so she can start cbt.
At one point several weeks ago her eating was so bad (refusing all meals except dinner, but then only taking 5-10 mouthfuls, then trying to vomit it back up...but I stoped her). The team we're looking at bringing in Intensive Nurses who would support me to support her. They don't do the work for me, more than encourage me along so I don't crack under the pressure and also encourage DD. We've got to a stage where she is eating lunch, dinner and a couple of snacks and absolutely no vomiting at all. She's refusing to engage with any of the ED team though, and will only speak to her MH nurse on the phone weekly. She's also refusing to get weighed and to attend clinic to get bloods done. I still have weekly video chats with her team to update them on her week and to soak up the support they give me.
I have started looking online at properties. The market in Scotland is still closed so options are thin on the ground. There is one which seems ideal as it's in DDs school catchment and very close to DDs best friend (same street!). It's absolutely tiny though but the best I can hope for if I want to stay in the area. I've had a phone appointment with a mortgage advisor and sent over all my financial records, so waiting to see how much of a mortgage I could get. He gave me a rough figure and the one I've seen is definitely within my budget. I keep looking at it online and imagining being there 
God I'm sorry for this long post. I guess I'm just pouring my heart out. I do really appreciate every reply.