Hey! Cute new frog!
I'm not exactly sure on the age, but I can help you with the nightcrawlers.
He seems to be pretty young so I would recommend a small chunk of them every night. He'll probably enjoy them for the most part, but don't be alarmed if he stopes eating every night, because sometimes they might not eat any. After about 3 months, he'll probably stop wanting to eat every night, and you could probably feed him 3-4 times a week.
More good staple foods consist of crickets and roaches, but the nightcrawlers should do just fine for now.
I'm fairly new to owning pac mans too, so we'll get through it together haha
Good Luck!!!