I have a right wriggler too. He's fine when he's fast asleep for the first few hours of the night, but after that time he spins in circles and goes up and down the cot - and he's in a sleeping bag! We don't have problems with his arms, but I have seen sleeping bags that keep their arms inside the bag, this might work for Chloe. Unfortunately I can't remember where I saw them, but it was on the net in the last few days when searching for things to help get a baby to sleep through the night.
Good luck, I know how the tiredness can really get to a mummy after a bad 7 weeks worth of sleep!
Debbie (Joshua's mummy - 19weeks today, WOW!)