Welcome to Frog Forum and congrats on your grumpy little buddy. He is very cute and has nice color. He is a Ornate Pacman.
When it comes to picking them up it is best done from behind. Just kind of gentley scoop him up. Be sure that before you even touch him that you wash your hands very well with a mild cleanser/rince really well then rince again with de-chlorinated water. Then you are ready to handle him.
These are fisty frogs so be careful and do your best not to harm hi. Even if he harms you.
You didn't feed him too much. Meal worms are bad not because of fat, but because their exoslelton is full of chitin that your frog cannot digest and if fed too many in either worm or beetle stages he may become impacted(sever constipation) and possibly die.
Get rid of the moss. It also is an impaction risk. If he accidentally swallows some it can block up his inside. As much as they love the moss to sit and burrow in, it is a risk.
Here is some very good info for you, Frog Forum - Pacman and Horned Frogs - Ceratophrys - Care and Breeding
Any specific questions just ask. There are several breeders and experianced keepers here.