And I would say horse is spoiled rather than "scared of almost everything".
While letting horse battle it out with being tied is sound advice, big difference in riding horse, and one this big. Tie horse solid to something and it has a fit and pulls back, could end up with hurt horse.
I've seen horses that would not tie. And none of them were "spoiled", far from it. Claustrophobic is more my thinking.
But one? Ended up stringhalt because of someone deciding to teach her to tie once and for all. Pacific Bailey bred QH mare. Nice mare. Ruined after that.
Another was Saddlebred. Hotter than normal, but only thing that broke her, if she stayed broke, was she broke crossties and flipped over in stall. She didn't do that again at the barn when I was there, so don't know if that stopped it forever or not.
And another QH mare, ties okay inside, but outside, has a fit and will pull until she dies I think. She was badly spoiled, and had bad tying accident when someone tied her as short yearling.
Drafts have enormous strength, and this would be a horse I would teach to tie by innertube method, rather than anything else, and then only if was absolutely sure that whatever tied to would not be able to be moved.
And even then? Might only work when the horse is tied to that, and not work if tied to anything else. Would not want to bank on horse being fixed of this.
None of us are there to see how you are handling this horse, nor how it is reacting, nor your facilities or your skills in handling horses for that matter.
I would strongly suggest you get someone on the ground there, that has experience with horses of this size, a GOOD person with horses, not some fool down the road in other words. Let them see what is going on and try to help.
Old Sorrel has Drafts and she may have some ideas.