don't put alot of water in it, just enough to cover the grain, beet pulp, and rice bran...I'll usually let it soak for 5ish minutes....should I let it soak for more?
Yes, definitely let it soak for more than 5 mintues!! Dry beet pulp may not cause choking, but it will expand in his digestive system and can cause problems there! Check with your feed supplier for the beet pulp to water ratio. Mine was always 1 part beet pulp to 4 parts water. I have heard of 1:3, but definitely you need more than just enough to cover! I always soaked the beet pulp for 24 hours, kept it covered during that time, and then added the dry grain or pellets or medication or whatever at feeding time. If it's covered, you shouldn't have to worry about the little creatures getting into it. I wouldn't soak the grain because it's not good for grain to sit in water for a long time. Add it later!
And, no, it doesn't sound like Sonny is a choke risk based on his eating habits. Slow and easy is the way to go. If you do have to feed him near other horses, try adding the block of salt to his feed dish to slow him down.