It sounds to me like the horse is serviceably sound and will continue to be so with maintenance that is within the scope of the OP’s vet.
OP, if you love the horse and are happy with how it’s gone for the past year, what you’ve reported doesn’t raise a lot of red flags for me.
Given your stated goals, do I believe that you could find another horse to enjoy for a lot less? Absolutely. But you could have found that last year, too. Are you at a point in your riding now where you might need a different horse? That’s something to consider. I’ve had a few horses that I thought were irreplaceable. In truth, they might have been, but I’ve found other horses that are wonderful in different ways.
What made you decide that you wanted this horse at this price point? If that hasn’t changed and you can afford the horse, go for it. The first lease payment is a sunk cost. I don’t know what the ramifications are for pulling out of a lease to buy contract so you’d need to review your contract (probably with a lawyer).
<<If I loved the horse, I’d do the following: 1) ultrasound that suspensory; 2) get the x-rays reviewed by a radiologist and review the report; 3) sit down with the vet and ask if you bought the horse and kept him in the same level of work he is in now, what would the vet’s plan be to get him sound and maintain him that way? Then ask yourself if you can live with that, and if you can live with the risk that it might not be enough and he might need an easier work load. >>
This is good advice but does require more investment on your part. My trainers have always told me to be careful about spending $$ to find out why someone else’s horse is lame, but you are a year into the journey and may have more interest in spending the money.
What does your trainer think?