3/8 inch crickets shouldnt cause a problem in frogs under two inches. The problem is that pet stores generally stock two sizes small(er) and large(r), which tend to fluctuate as weeks go by between orders. What came into the store as 3/8 inch crickets end up being 3/4 inch crickets in a couple of weeks, leaving the consumer with no option to buy smaller crickets.
Ordering your crickets online may not be much help as they will grow just as quickly if you order in bulk. The only options are if you have a reptile specialty store that carries all six sizes at all times or breeding your own. Breeding crickets is a kind of a pain in the butt, which makes the slow growing dubia a much better option though they are more expensive if you arent breeding them.
I do not think you are facing a prolapse concern or a an impaction concern if you are feeding nightcrawler sections that are equal in length to the width of the frogs mouth.