sorry didnt want to read and run but i only have 1 idea that might work.
do you have family near by?
if so do it, move in with them, just for a long weekend but dont tell dd and oh how long itll be and maybe your daughter and oh will see how bad they have been and maybe they will try a bit harder to make things a bit easier for you when you come back.
i know its drastic but it sounds like you need a break from them and making them suffer a lil is well deserved i think.
even if it doesnt work at least youve had a time out for a while.
i hope everything gets better as you dont need the stress at the mo.
take care
xxx