Forgive me for my opinion on this I also haven't been able to read everyones replies yet (that's what bedtime is for!) I believe you do want another horse BUT I do not believe that you want this horse for the right reasons. After following your story for so long it's pretty obvious to me that every inch of progress you make must feel like a mile. Trust, in your shoes I would also be gagging for something FRESH, a new project to breathe life into where I might be able to get real results without slogging it out for a year or more.
I'm all for rescues you know that haha but I do ask that you be honest with yourself about your goals. I bet there was a time you thought you would never give up on Kodak. But here you are - and btw no shame, no judgement. Not everyone is cut out for it as I sure know I'm not interested in a Kodak-esque horse to ride and die on. She just suits a very specific type of rider I guess. But let's say you get this horse, you fall in love. Her heatlh deteriorates. You can't rehome her. I have had plenty of animals where I have been broke and tired and a part of me just wanted to not have to be responsible for. Which is pretty human I think, to want a break. You deserve a break - not another liability.
I also want you to be absolutely sure you are willing to risk your finances, your time AND your friendship. This is friendship-killer material right here. This might seem strange but I am less likely to trust a friend when it comes to animals/horses as I know they are preying on my VERY WELL KNOWN weaknesses. They might be the best friend in the world but when it comes to SELLING or even giving freebies you cannot deny that they have an agenda. Tell me honestly - do you think, from the bottom of your heart, that they are setting this up for your purely out of goodwill and with no benefit to themselves? I can clearly see you being taken advantage of - because you are keeping a "crazy horse that no on would have the patience to deal with so ofc you would keep the sick one". You also must have money. Look at how much you invest in your horses health and daughters comp life. "Who can I give a nice horse that is sick but deserves a good life with someone that can afford her medical bills?" BINGO. At least you can expect sellers to be dishonest to a point. Then comes the additional baggage of obligation... and guilt... I am not saying your friend isn't a good person or doesn't mean well. But when it comes to selling, a seller as to make a profit somehow (money or otherwise), friend or not.
Sorry came down super hard you know it's just how I think <3 I think you are an amazing person who deserves so much good. So with all the above out the way? You willing to risk all that? Tight contract, a steel heart and give it a shot. Regardless if you keep horse or not or even if friendship goes to pot, at the very least you and the rest of us can be consoled by the fact that said horsey is gonna be very well taken care of and loved! And there is always the chance this horse might be the best horse of your ridden life even against all odds...