Help! How many pellets do I feed my turtle

Hi!

I got a turtle last month from a pet shop, he was very small, and at first I would feed him outside his tank and give him 2 pellets. Now, he’s a little bigger, but I feed him around 2 to 3 pellets- but he still swims up against the glass, and normally he does that to get my attention for food. This is the second time I’ve feed him today, and in total he’s eaten around 5-6 pellets in total. Is that a safe amount? How many pellets should I give him max? Please let me know, thank you!

P.S the last two pictures are from when I first got him!

Also any advice on how to get the glass a little Cleaner without using chemicals?