Yes, I know the feeling. I have my horse to do with as I please, so I don't feel too stuck. However, after having the past four years off from lessons and showing because of college I wanted to get back into doing something else with my horse besides just riding for fun. I tried working with a couple of horses in my barn, only to decide that neither were sound enough for real work. I then convinced my old trainer (who hasn't been involved in horses for a couple of years) to give me lessons, but I'll just say that the quality of the lessons were not what they used to be and were no longer worth the time or money. I tried to get a friend of mine to help me work with my horse's loading issues, but she proved to be less than reliable. We finally got the occasion to bring our horses to ride with a lady down the road, but my horse was such a butt getting into the trailer that now she would probably never offer to take us anywhere again, and I don't have access to another trailer for training. The prospect of me acquiring my own trailer proved to be a bust. I tried to find a dressage trainer that would be willing to come to my barn for lessons, but it's pretty slim pickings around here. The one guy that seemed somewhat willing has issues traveling so far, but said that he would get back to me when time freed up. He hasn't.
I do enjoy just playing around on my horse more than anything, and I don't think I'll ever lose this love. I just feel as though I'm stuck in a rut that I'll never get out of until I either get the money to buy my own trailer (at least a couple of years), or move barns. The barn options are pretty limited, and i'm not guaranteed transportation to any activity or trainer anyway. It sucks, but I'm thankful to have the horsey opportunities that I do have at the moment, and I'll try to never forget that.
Now on to your sticky issues- have you tried looking for a therapeutic riding center in you area? At the first barn where I boarded there was one that did lesson twice a week, and they were always looking for volunteers for their program! The volunteers assisted with grooming/tacking the horses, handling the horses and riders during lessons, and untacking/cooling the horse afterwards. This would be a no-cost option for you to really focus on handling a variety of horses in different situations, both on the ground and during lessons. You'd also be doing a wonderful service for the kids and adults in the program, and whoever is running the program would be very grateful!
Perhaps you could also work out an arrangement with your trainer so that you could have one lesson every other week, and two lessons every other week. An average of 1.5 lessons per week. If you are a committed rider that regularly attends and pays for lessons then the instructor may be willing to work something out. If not, then maybe you should consider putting money aside each month for a partial lease of a horse. I don't know if it's financially possible (especially since you should still take a weekly lesson), but if you try to cut costs elsewhere you may be surprise what you come up with when you put your mind to things
This would give you a LOT more freedom to do what you want and do things other than just arena lessons, such as hacking in the pasture with barn buddies :)