Use smaller worms or breed smaller species of worm. There are literally hundreds of species of earth worm and some grow huge, and others are tiny. Find a species or strain that grows to about 1 inch long and then you don't have to chop them up for the Axos.
You can also feed Axolotls on raw or cooked prawn, bits of fish and other marine based meats (squid, mussel, etc). They also eat brineshrimp, mysis shrimp, daphnia, rotifers and anything that falls in the water. Try to feed them a variety of foods so they don't get hooked on one type and so they have a more balanced diet.