Yes nightcrawlers are way better then crickets, but for some it takes time to get used to them

are supplementing with ca/vitd3 and multivitamins and if so how often?

you gotta do smth about humidity, yours is way too low, you gotta keep it at around 75 (70-80%), but never lower then 70.
How big is a frog exactly? And yes picture of a frog and his enclosure would be very helpful.