Yes, Bed-a-beast is the same thing as eco-earth, and both are OK. They have a fairly neutral pH. You should not put 12 crickets in at once, particularly if the animal isn't eating. As I mentioned, crickets will chew on salamander skin if there is nothing else in the tank for them to eat (poor sal). It's possible that your sal is eating a few of the crickets, but doesn't need 12/week. I'd say put in 1 or 2 crickets and don't add more until those are gone. Also, put some cricket food (like a piece of potato, lettuce, or carrot) in the tank so the crickets have something to eat.
You need to have a small setup where you keep the crickets alive and healthy until you need them. The crickets need moisture (like a piece of wet sponge) and something nutritious (thus the added nutrition is passed along to the sals). Feed the crickets carrot and other veggies. On top of that, you should be dusting the crickets with a vitamin/calcium powder immediately before putting them in with the sal. This is because crickets, although rich in protein, are very calcium-poor, and this can have very bad effects on any reptile/amphibian that eats mostly crickets long-term. Earthworms are nutritionally much better.
