Don't get discouraged. Keep forging ahead with your eventual goal of buying a place in the country for you and Katie. Of course you have to sell your current house now, and I get that it's not a good time to sell. But keep at it. You just never know when all of a sudden, a door will swing wide open!
In the meantime, keep looking for a better boarding situation. I like hlg's idea of looking at private barns. Knock on some doors if you have to - explain your situation. You are paying very good money for a horse you do not get to see! Don't give any details about where she is so you're not going around bad-mouthing your current stable, just explain that you would like to be more involved in your horse's life. Someone with a small, private barn might welcome the extra income and/or the extra help around the barn! Offer to do chores, to look after their horses so they can take a vacation... and if nothing comes up for a while, you know Katie is ok. When you see her at your appointed time, tell your you're working hard to make your dream come true and that someday, she will come to live with you in the country where she will wake up to the birds and spend her days walking down country lanes instead of busy city streets.
Chin up, you will find a solution eventually. You've had a rough go, but you got a glimpse of what might be... keep reaching for it.