In our collective experience a normal horse (or a well controlled IR horse) being fed only hay will have an insulin below 20 (and usually more like 10-15).  So Sunday's results show that he is indeed still IR and needs to be treated as such although he is not in danger of laminitis right now.

Given that CSU lists their reference range as 4-8uIu/ml that's a fasting range so you have to go by what we know, not what they use.

He can stop eating hay for a few hours (2-3) and that will not be considered a fasting result but to compare apples to apples you do want hay in front of him until the blood is drawn.

I would definitely keep an eye on his diet and monitor fat pads and crest but I think you're managing him well at this point and adding exercise back in might help bring his insulin down even more.