It IS hard, especially when you're getting no sleep. Sorry to hear you're feeling rough. OK, let's deal with things in turn.
Feeling low: it is really common for hormones to change even well after the birth, I think weaning times are particularly common. Can you keep an eye on your mood somehow and see if get worse/better?
Sleep: not any surefire advice on this one - my kids have all been broken sleepers. It does get better and you can find advice in books and on here - and don't let go of the fact that you've had some success with bedtimes, you can also gradually change things at night. Are you sure the sleep is a general pattern? We have a tendency to blend everything into one, he (DS3) has a teething or ill phase and we remember it always being like that; then he goes back to how it was when it wasn't sore, and we go 'oh yeah, it wasn't always so bad...'
Also have you tried giving Calpol to see if it is teething pain? Have you tried upping the breastfeeds in the evening? Weaning is a common time to increase BF - guess they maybe find change a bit insecure and your supply might have dropped a bit too. Try two or three feeds before 9pm and if appropriate a dreamfeed at 11 and see if that helps? Or a cup of milk or bowl of porridge at bedtime also? This got DS3 through till 11 feed some nights.
Food. Can you tell us a bit more about the crying through meals and not eating very much, taking forever to eat...? Sounds like this is harder for you all than it needs to be.
You and the DH: could he work somewhere else while the baby is so all over the place? Borrow an office? Go to the local library?
And can you come up with a plan to give first you, then both of you a break? Could he take the baby out in the pram in his lunchhour and you have a lie down? You need to find a trusted babysitter I think. someone recommended a great website on MN the other day - think it was called findasitter.com Failing that, try your local nursery - ask the manager if you can put a sign up to see if any of the nursery nurses want a bit of extra money? Or your local nursery training college? Or ask neighbours - especially non-working older women - if they'd be interested every once in a while?
Aim for you and to have one evening out a month?
Alternatives might be find a gym or shopping centre that has a creche and you and he just spend an hour or two hanging out.
Good luck and please post again...