Most people say only to feed pinkies on a monthly basis, as a treat for a little extra calcium. I have two healthy frogs though that ate nothing but 1 rat pinky a week for the last year atleast so.. it's really up to you. Pinkies are high in fat and I personally would stick to the monthly rule. I haven't fed my frogs pinkies ever, though I will probably get them some as a treat one of these days.

Edit: The best staple diet for pacman frogs is nightcrawlers. Much easier to take care of than crickets, just buy a box/tub of them and keep them in the fridge. Easy as that. Lots of people say Walmart has good worms, I don't shop there so I wouldn't know. Just make sure if you do get some they don't smell funny or have any funky dyes. They should have an earthy smell. Don't get red wigglers either, just Nightcrawlers.

You can't really get your frog to croak on command, mine only do it if it's raining or there is another frog calling (sometimes) or just completely random. They do it when they want to do it.