at one point I swear she couldn't breathe, there was heaving, sick, dribble, a very red face - is that not just torture?
I know it's awful and you feel like a witch if you don't try to make things better but you are doing the right thing by not giving in. Just be calm and ready to reassure her.
How though do I handle the fact that she snatches her hand away and then runs off at high speed? If I hold her clothes/any part of her she literally throws herself on the floor, (usually head first), she twists, prizes my hands off, bites, kicks, screams like she's being abducted... literally anything she can do to get away, same with picking her up, she twists, screams, throws herself backwards and it's hard to hold on to her without hurting her
She really goes for gold doesn't she?
You aren't going to hurt her just by holding her. Let her throw herself to the ground and scream all she likes. She won't be able to get away from an adult. Make sure you're not holding her by her hands or wrists but by her longer bones in her arms just to be on the safe side. If she's trying to bite you hold her facing away from you with your face out of the way of the back of her head. She will scream blue murder but you need to stay calm. Hold her just enough to stop her running off and just keep doing it until she calms down. Don't get cross or try to reason with her as she probably won't be able to think straight anyway. Once she's calm and ready to hold your hand move on cheerfully as if nothing has happened.
The thing is you can't avoid tantrums. They will happen wherever you set the limit and you will have to set it somewhere. If you give in now she will just let rip at the next thing, then the next and at some point it will be something it's not safe, reasonable or within your power to give her.
You've done some good ground work towards getting bed time sorted. Do exactly the same tonight and she will get the message that Mummy can wait as long as it takes.
There are some interesting threads about getting rigid children into car seats and buggies with descriptions of some novel techniques. Again, try to make sure you have time to wait quietly until she gets bored and is ready to cooperate. Staying rigid takes a lot of energy and is hard to do for very long.
Life is generally much pleasanter once they've got the message 