I don't know if these things will work for you, as my girl's circumstances were different, but here are a couple of things that have worked with us when they display challenging behaviour.

Turning things into a funny game - sometimes if they don't want to do something, or are doing something undesirable (like banging their head) you say "Oh dear! Poor wall! Don't hit the poor wall" and the idea is to just get them laughing. If its putting shoes on - "Come on shoes! Go on DD"s foot!!" etc etc

Having special "stomping" music - when they are grumpy/upset I'll say "do we need to stomp? come on, lets put the stomping music on and get our grumpies/angries/whatever's out" at the moment our stomping music is "crazy" by Gnarles Barkley. This just gives them an outlet for whatever theyre feeling.

As I said, these things may not be appropriate for you to try, but I thought I'd share anyway. I hope things improve for you soon