Hi Gemling
You're certainly not alone. I recently had two 3yo ponies and a TB at home and have been through a similar situation. As much as we love them, horses always seem to do their best to test us! Off the top of my head, i've had bolting, running through post and rail, snapping electric fencing and dragging the posts around the field.
It sounds like you are 100% doing what's best for them in terms of stabling and turnout. A few things that really helped me were:
Feed. Have you changed feed since she stopped working? Even certain cool mixes can be quite heating. Could it be that she now has too much energy? Dengie Hi Fi Lite, Allen & Page Fast Fibre and Equilibra 500 work well for my TB, low in sugar :) He's much calmer since changing.
Routine. Horses thrive on routine and can become anxious if things change. Try to make sure you turnout and bring in, feed etc. at similar times each day.
Leading. My TB was also headshy and although much better, he has a very strong fight/flight response and will start lifting his head when he wants to go. I found pulling on the rope or being forceful generally made this much worse. Instead I keep the rope quite loose, but still tightly held in my hands, to give him his head (and prevent him from fighting) and I make him stop if he starts trying to walk ahead of me (an elbow/ arm pressed against the chest helps if you're really struggling to keep control). I know this goes against your instincts, and I wouldn't recommend doing this if you feel unsafe, but after a few goes he soon got the idea and became much more relaxed when leading and he's now absolutely brilliant. You might want to practice in the field if you think that would be better? A reward is a nice incentive for a sensible walk :)
Gloves. Rope burn is the worst!
Circles. If it's safe to do so, then you might want to try turning her in a circle if she starts picking up pace. It may help teach her that she doesn't get anywhere by rushing ahead. Obviously I wouldn't recommend doing this if she's kicking out etc. I also turn a circle back towards the gate when I turn out. If I just walked straight into the field and then tried taking the headcollar off etc., he would try to bolt off, but turning the circle made him wait and listen to me while I took everything off and then he got a pat and went on his way.
Calm. I know it's hard when she's making you nervous, but try and approach her calmly and confidently, avoiding any quick movements. Have exactly what you're going to do (which field etc.) in your head and stick to this. If you can, try and bond with her when she's in her stable or turned out in the day. She may have been used to more attention than she gets now.
It might also be worth having a think about the pony and if it's easier to turn the pony out first while the TB is safely stabled and then go straight back for her or perhaps it works better the other way around? Either would be safer than trying to manage both.
Sorry for the rambling post, but I totally sympathise with you and hope you find something that works for you.