Generally speaking, a horse needs to consume 1.5% - 2% of it's body weight in forage every day.
Forage means grass and/or hay.
Feeding roundbales is a sticky wickett and not-at-all efficient when only one horse is involved.
If the horse is a fairly easy keeper, it might stand there and eat until it's hooves are pointing skyward. I have one like that --- he is insulin resistant.
I wouldn't free-feed hay in the stall either, because of the potential mess and waste. "Free-feed" to me means you want to put enough in there to last him until you visit the following day.
That being said, two flakes of hay per day is not enough for any horse, unless it's a Mini. Further to that the flakes need to be weighed. I was really surprised at the huge difference in the weight of flakes when I had to start weighing them for my metabolic horses.
If I were in your position and not able to move, I would get a couple small square bales of quality mixed grass hay, stand on a scale to weigh each flake and feed him about 18 pounds daily<---twice a day would be best so he doesn't waste it.
I wouldn't dream of just feeding two flakes a day. Especially if he's getting bagged feed; which he doesn't need because it doesn't sound like he's in hard training for anything at the moment. They are grazing animals by nature and need the forage moving thru their digestive system.
A ration balancer with a vit/min supplement would serve him much better. Things like Nutrena's Empower; Purina's Enrich 32; etc.
Please check his manure
It's ok if his manure is brown (as opposed to olive) because he isn't on pasture. It should have a glistening moistness to it and while it should be a solid conisistency, it shouldn't be hard and it shouldn't be dry.
Sorry, I know that's gross but it sounds as if he's not getting near enough forage in him, even if the B.O. says his weight is fine. Again, I'd be wondering what and how much is going into his feed pan
Back to the round bales --- we never fed them when I was a kid on the farm --- not even to the dairy or beef cattle. Grass was free-range but hay was controlled.
I don't believe in roundbales for my horses as there's four and they can't eat that bale fast enough before it turns moldy, and/or someone that goes "squeek squeek" and has foot-long tail moves into it.
I throw hay off the small squares, every morning, according to their needs.
Amazingly, I still have green pasture. They walk right past the 20 lbs I throw (for four), wander 22 acres all day, then come in around 3:00 for water and head to the hay piles. They aren't hungry and there's no point wasting large amounts of hay. Just flush that money right down the terlet
Oops, others answered before I got this typed:)
Ditto the slow-feeder hay net as long as can be safely hung so he won't get caught in it. One of my IR horses has to have his hay that way.
Hope this helps