Hi there!
Glad to know that you care about your frogs.
Yes, those are probably African clawed frogs. About how big are they?
The smaller one is probably a male, but you should be sure he eats just to make sure the big one isn’t just mean.

I used to have a pair one female one male, and the male was 2in and the female was about 3. They were only one year old when they passed under circumstances out of my control, so I don’t know their exact adult size. The females do grow bigger than the males but I don’t know if they stop growing or not. However, I have seen some pictures of ones that appear to be as big as 5in. As for age, the oldest one I’ve heard of was about 10 but even that was very very old. Yes they will probably grow more when their setup and feeding is better.

Yes, a 29 gallon is awesome!! However, you will want to only fill it up to about 9 or 10 inches max. They like shallow water.

Yes, you can give them pellets. That’s what I fed mine. They do like freeze dried bugs and will also occasionally eat live. Hand feeding or tweezers or forceps is fine as long as the tweezers/forceps have rounded ends so as not to injure the frogs.

I used a sponge filter for awhile, but either the filter was just not good quality (which is entirely possible) or sponge filters are just not great for this species - either way, it couldn’t handle the frogs’ waste very well. However sponge filters are pretty quiet and frogs like quiet filters because too much noise and vibration gives them a sensory overload and causes stress. So if you get a sponge filter that is marked capable of cleaning the next size up - i.e. 40g - you should be fine.
An air pump just puts bubbles into the water - you’re not stupid at all! They don’t need an air pump. In fact, too much oxygen in the water can harm these frogs - air pump not recommended.
As for the filter, just rinse it out really good in the dirty tank water before you dispose of it. I would clean/replace the filter about every 1 to 2 months. These frogs make a lot of waste. The question on whether you should just clean or entirely replace the filter material depends on what filter you get.

I used sand and they were just fine - these frogs like some sort of substrate to rest on. However I would not use any type of gravel at all. It is amazing how whatever size of gravel you get, they Will try to eat it and most likely choke or otherwise harm themselves. Sand is much better.

Great job!