I agree with the others who have said to do 'your time' in the hospital now rather than risk being readmitted. Your best shot at being astride a horse in 90 days are to think of yourself as being in training. You have to be able to breathe before you can walk, walk before you mount, and post before you can lope. (wasn't that clever, sort of?)
Also, I'll share with you that cottage cheese is your friend. K2 is a substance that is found in foods, also available in a supplement, and is required for calcium to do its job in rebuilding bone. K2 helps the body lay down a lacy network of tissue upon which calcium is deposited to make bone (layman's terms). New research shows that K2 is abundant in fermented foods (cottage cheese, curd cheese, sauerkraut, and natto - fermented soy). When taken with D3 (note the 3) available in pills, the remodeling of bone is even faster.
I broke my arm 6 weeks before my son's wedding, and everyone was sure I'd be in a cast for the pictures. I ate cottage cheese every day and the doc was amazed at how fast it healed. Apparently it was broken even worse than they originally thought but it healed enough that I was out of the cast in 5 weeks. ETA - got this good advice from my ER doc, who raced greyhounds and this is their trick to heal their delicate bones.
Also, I'd like to say that the idea of feeding chocolate to the nurses who bring your meds reminded me of clicker training! I'd glad you're having such good results!
Good luck with the decision on Mr. Big. I fully support you in being cautious and careful, and it's not anyone else's business what you decide to do. There will be folks who strongly agree or strongly disagree, regardless of what you decide to do - you know your horse and you know that you can't live with yourself worrying about him in someone else's hands, or worrying about him hurting someone else. The worst almost happened to you; if he leaves your control and people know that he is an experienced, well-trained horse, they could take chances with putting someone up on him despite his history - a less experienced rider than you might end up on their final ride. I wish you peace with whatever you decide.
Finally, I'll try to keep watching for your updates. I'm sending healing prayers your way, and I hope you continue to mend, and mend quickly.