So for starters it would be best to turn off your aerator. Betta's love nice still smooth surfaces because they have labyrinth organs which allow them to breathe air. If there's too much surface movement it makes it a little more difficult and makes them agitated.
So there are a few things that could be causing his bloat.
The first as over feeding which you've already seen and tended to which is great! The second however being the type of food you give him. Anything Freeze-dried is not goo for Betta's because, yes it's high in protein, but it also promotes constipation. But it's also the quality of the foods you give him, I an guarantee you that your TetraBetta food has at least 2 "filler" product in the first three ingredients.
The things you want to stay away from in foods are the fillers which are any wheats, other grains and corns. You want things like Whole Salmon, Krill, Shrimp, and stuff of that like. So I would suggest trying to get him on a higher quality food like Omega One Betta pellets or New Life Spectrum Betta Pellets, both are pretty darn good. I have both but the bulk of my food is NLS because my Betta's absolutely adore it! It's also a smaller pellet which helps them to be able to actually eat it, sometimes the pellets are too big and they can expand in their stomach.
That's a little experiment you can do: take a pellet with a cup of water, throw the pellet in and watch it over about half an hour to an hour and watch how much it will expand. That's how much it expands in your little boy's stomach.
Then the third is just sometimes certain fish are prone to constipation no matter what you feed them. Two of my double tails are both prone to it so I only feed them 2 pellets and I wait for them to poop over a day or so, if I haven't seen them poop yet, I don't feed them until they do.
I also fast all of my fish two days out of the week (mostly because I'm not there) but in those days it helps clear out all of their digestive tracts.
But something you can concider using is Epsom Salt. It's a laxative that you can find in the first aid section of your pharmacy/wal-mart (I got my bag for 89 cents!) but you want to look for something without additives and with no scent. <---that's key!
So for a treatment you can use 1 teaspoon per gallon since it's only mild, we can use a mild dosage.
Pre-dissolve the salt in a different container, so you'll only be using 1 teaspoon since it's a 1 gallon.
Mix into his water a little bit at a time, preferably over the course of half an hour or more so it doesn't shock him.
Don't feed him until he poo's, then you can do a 100% water change to remove the salt (it doesn't evaporate) and continue on you way!
But first I would just not feed him for 3 days or until he poops. The poop should be orange/brown and solid, kind of curly looking.
There's also the blanched pea method if you like as well. That should be used at the end of the 3 day fast period. Take a frozen pea (no fresh ones) and put it in a container with conditioned water, or just take some from his tank. Microwave it about 30 seconds, shell it and take the two halves out. Feed him a very tiny piece of the half, no bigger than his eye! He should go right for it and then don't feed him until he poops.
Also just a comment about your water changes, you are doing good so far! But it would be best to do your 50% every few days but do a 100% each week so that bad stuff doesn't build up in his tank. Also remember to scoop out any uneaten food!