LittleAmy, of course it is not unreasonable for your husband to watch his baby, too! The key is in the latter part of the sentence: its his baby, too.
Some days when DD was small I would literally hand her over to DH as he came through the door and go to bed for an hour. He understood. His job is physical and gruelling and he's on call 3 times a month for a week at a time. But my life was physical and gruelling and I was on call 24/7. He supported me.
You've asked when it will get better/easier. Well, everyone is different, but for me 6 months was the switch. It was then that we sussed nap times. At 4 months DD was hard to settle. I would sit beside her cot and hold her hand and shush her when she fussed and if I was lucky she would sleep for 30 minutes at most (rarely) after I left the room. I remember once trying to treat myself to a heated demi-baguette (yes, that was a treat!) for lunch and no sooner had I put it in the oven she woke up yelling. I remember standing in the kitchen, bursting into starving tears and shouting "I just want a fucking meal!" 
Anyway, around 6 months I took to heart some advice I read on here which was that if I ever got to breaking point, to remove myself from the room and take some deep breaths. After a 2 hour crying jag as she tried to sleep I broke: I left her in her cot and went to the bathroom to wash my face. She stopped crying and slept for an hour. After that I took five minutes to settle her and she would go to sleep. I guess I effectively let her cry out to sleep, although I was with her for 99% of it. I never thought I'd do that, but it kind of worked.
So from 6 months it occured to me that I could leave DD to go to the loo or fix myself some food or something like that for me. If she shouted in indignation, then she shouted. She survived. I would only be gone 2 minutes. Anyway, 2 months after that she was crawling so she'd follow me.
I also think that by 6 months when I started baby-led weaning she became much more of a sociable little part of the family. You only have 2 more months to get to that.
I don't think you and I have/had it much different. You describe your life with DH much like mine with my DH. We did get that back after those first 6 months. But he supported me throughout the 1st 6 months, too. That's the key, really, support. As previous posters have said, you don't sound like you're getting that from anyone, so I can fully appreciate your feeling lonely.
You mentioned that you feel your DH can't understand your frustrations because he has a wage coming in and a job to go to and adult conversation? Are you on maternity leave from a job? Do you have one to go back to? When my DD was 9 months old I went back to work part time which was perfect for me.
I work Monday, Tuesday and Wednesday mornings with DD in nursery for the duration. She started going one morning a week from 7 months to get into it, and having that morning to myself was bliss. I got to shower during the day and do housework in peace. And even sit down with a cuppa for 10 minutes. Have you thought about that? Just having one morning of not feeling like you're at your DDs constant beck and call?
I don't know whether you've said this, but whereabouts are you? I'm in Oxfordshire if its nearby?
I'm sorry for the huge post, but your situation has moved me so much.