Feeding too much or little?

My gelding is stall kept. Has too until he is sold, and crawls under the wire fencing. Yes the fence is on, do not know if he's getting shocked or anything. Didn't have that problem with the last owner. Thing is he does get hay and water and half a scoop of Horseman's edge 12% of sweet feed. I switched his feed because he got the southern states brand of textured feed which was the cheapest crappy feed. He's a lean pony, not going to get any fatter, doesn't need to be obese. I just need him staying at a healthy weight. My papa told me I wasn't giving him much hay and giving him too much feed. I do ride him every day and he's out for 2-3 hours, I ride him for an hour. I don't know if I am giving him too much or not enough. I will call a vet here soon and talk to them about it.