Sorry to hear about your DH. Your DD may be picking up on your stress and sadness - DS is 2.4 years and really sensitive to my moods.
In fact, that was one of the reasons we're stopping co-sleeping right now because I'm 6 months pregnant and very stressed with the pregnancy/toddler/FT work. Sometimes I lie awake for hours at night...and so does DS!
What we're doing (which, fingers crossed, is actually working) :
DS has a single bed in his room. We bought a lovely Thomas the Tank Engine duvet set (he doesn't actually use duvets or covers of any kind, but loves Thomas!)
I made a poster, with photos, with a clear bedtime routine (milk, brush teeth, night nappy + pyjamas, DS turns light on in his room, 2 books, Mummy turns light out, DS goes to sleep in his bed)
I also made a reward chart and bought special Thomas stickers.
If DS goes to sleep in his bed he gets one sticker and if he stays in his bed all night he gets 2 (when he wakes up in the morning)
We explained very clearly the deal to him (he sleeps in his room, I sleep in my room). He was very upset the first night and really didn't want to get into bed. I ended up getting into his bed with him and waiting for him to go to sleep, then creeping out (not easy when 6 months pregnant!). Everytime he woke I was in there immediately, though he wouldn't calm down until I lay with him. Each time he fell asleep I left.
We had 3 nights like that where each night he was happier going into his bed...as long as I lay with him. Not easy for me.
Eventually my mum (who looks after DS whilst I work) told DS that mummy cannot get into bed with him but must sit in the chair whilst he goes to sleep. She repeated it many times to him all day.
That night he asked for me to get into bed with him but accepted that I didn't! (much to my surprise). So now I sit in the chair next to his bed whilst he goes to sleep.
We're 6 nights into it and he still takes at least 20 - 40 minutes to fall asleep but is waking up less in the night and stays awake for shorter times (first night he woke 3 times and took up to an hour to go back to sleep, last night he woke once and fell asleep 5 minutes later).
We really go overboard in congratulating him the next morning, with stickers, telling granny (who then tells anyone we have playdates with so he hears all the time how well he's doing). We also gave him a left over Christmas present after 2 nights, which he was thrilled about. He'll be getting another one in a few days time too.
I had serious doubts about it working but was desperate. It's not completely fixed (still can't leave him whilst he's awake) but is getting much much better.
Good luck