I think you have perfectly reasonable concerns about the lack of turnout and exercise. You know your horse better than anyone. Some horses just DO NOT cope well with alot of stall time. I board now but I also had my horse at home for 4 years so I can completely relate to your concerns. I have owned him for almost 9 years now and he has always had 24/7 access to his stall. The longest he has been in a stall is 4 days and at that point he becomes dangerous to handle on the ground nevermind ride.
Like your horse , he prefers to be able to go in and out. He can handle a day or two in a stall and I think he would be fine with 12-14hrs turnout per day and then stalling at night but the fact of the matter is very few barns offer that much turnout in the winter months in my area. They also keep them in for every little rain sprinkle. The barn he is at now is the exception, not the rule. I know my gelding would not be sane nor happy with the amount of turnout you describe in combination with only working 2-3 days a week.
It is hard to go from having them at home and having 100% control of their care to boarding so I can relate. You really have to trust the judgement and knowledge of the people caring for you horse. It was a tough transition for me. I do enjoy it now though to be fair my horse is only 1.5 miles away and I see him every day.
I agree that your lease situation does not sound fair on your end either.
Definetly agree about that, if the weather is no good there is no reason to not spend at least 8 hours outside every day. You might find it difficult to match the right leaser along with 24/7 turnout. It can be hard to find in addition to an indoor arena and a trainer.
I think you should keep networking to find the ideal lease situation that will keep you comfortable and ease up your workload at home and your pocketbook. People want easy to ride horses that are also easy to look at! I think your best bet would be to find either a competent junior rider who boards with a trainer who has a program that you like or an adult rider. There are plenty of adult riders who are out of the game without a horse that would dote on yours. If you decide you want to sell an adult rider could be the way to go, someone who would go from a lease to buying.