Let's stop worrying about talking about other members and let's focus on helping this frog.

Welcome Rob.

I highly recommend filling that 5 gallon up, not half way. I had frogs in 22" of water in my tanks and they thrived. At 3 years old, your frog should be full grown and depending on gender it should be over 3" of body length (nose to bottom, not including stretched out hind legs) if a male and over 5" if female.

The small tank, poor diet and inadequate water volume have stunted his growth. The 5 gallon will be a much healthier environment for him. While switching, I would not move over the gravel as he is looking rather rolly polly as it is and has problem ingested some which can be quite damaging to their insides. Opt for a bare bottom tank or a thin layer of sand in the new tank.

If you are going to keep not filtering, please do a 50% water change every three days. This will help him immensely - only treat the water with a fresh water conditioner like API, do not treat the tank with salt, pH buffers, ammonia remover etc. The fresher the water is, the more fresh water creatures appreciate it!

You already greatly improved his diet so well done there. Instead of freezedried brineshrimp try switching to the frozen brine shrimp cubes. Just cut off a small amount from the block (keep the rest of the block frozen), thaw his portion in tank water then feed. It is easiest to feed using a little plate on the bottom of the tank and squirting the sinking food onto it (the brine and depends on which type of pellet you use - some float, some sink). Feeding in the same place every time teaches the frog where to go when it smells food (their vision is awful!) and it keeps the tank cleaner by not having food scattered all over the place to be missed so it rots. Rotting food fouls the water.