Mealworms are a serious impaction risk and shouldn't be given to pacs. Waxworms aren't much better. Their exoskeletons don't really digest at all...

What sounds risky? Bait-shop crickets? I'd agree, most of them are. But if you find a store that breeds their own, then you can find out exactly how they're being cared for and know whether they're safe. I definitely wouldn't just walk into a bait shop and buy something to feed any of my reptiles

Seems like a lot of pacs aren't very interested in nightcrawlers at first. You can try rubbing the nightcrawler on your frog's lips; a lot of times they will get annoyed and bite it, then keep eating once they realize it's food. Once they start eating them, they usually love them.
You say 'earthworms', are you sure you're getting nightcrawlers? Most places don't sell actual earthworms, only nightcrawlers and wigglers. Make sure you aren't getting red wigglers; nothing really seems to like those