Substrate and Worm help

I found some mold in my Tiger's tank and concluded that his tank is too wet. I haven't been misting the tank much or anything but the soil is holding in the moisture too well. So my question is, can I mix in a filter sand with the soil? Would it keep the soil from becoming too wet? I plan on getting some Eco Earth coconut fiber once I use up the soil I bought so the sand/soil will be temporary.

Also I tried to feed my Tiger some earthworms but he doesn't seem to like them. I cut them up in pieces and he only ate maybe half a worm before he refused the rest of them. They are bait shop worms labeled dew worms but they are basically just regular earthworms. I was thinking perhaps the earthworms produced some sort of nasty mucus or something when they were cut because he started rubbing his nose along the ground after eating them and they did look a bit slimier after they were cut. So I thought I might try not cutting them, but they are very large. He's about 8 inches long and the earthworms can stretch out to be just as long or perhaps a bit longer then him. Would that be too long for him to eat? Other then earthworms, the only other foods I can get a hold of are crickets and maggots

I haven't heard of "dew worms" but the worms sold as "red wigglers" or "jumpers" here, Eisenia fetida, have a strong odor and apparently flavor too. I've had some salamanders show similar signs to what you describe after eating a wiggler and refuse to try them afterwards. Nightcrawlers, which are larger and less active, seem also to be more palatable. A tiger can easily eat a nightcrawler longer than itself, though it may take a while to get the whole thing down.

What kind of sand? It's probably OK, but an easier alternative might be to keep the tiger sal on damp paper towels until you get a substrate you are happy with. Instructions for keeping on damp towels are in the tiger caresheet, under adult housing:
http://www.caudata.org/cc/species/Ambystoma/A_tigrinum.shtml

Are the worms light gray in color, or reddish-brown? If they are light gray, these should be ideal. Some sals do seem to dislike the slime on worms, so it helps to dab off the slime using dry paper towels, or feed the worms whole rather than cut.

Its a very fine filter sand. I did have him on paper towels when I first got him but he really does like to dig around in the soil so he'd probably be happier with the soil and sand mix. And it might take me some time to get the coco fiber since our small town doesn't have such things. I probably have to order it from the net.

As for the worms, I did research dew worms and I believe they are just another name for earthworms or nightcrawlers. They are a reddish-brown sort of color. Tomorrow is his feeding day so I'll try wiping off the slime and giving it to him whole and see if he eats them better that way. I did find it a bit interesting to see that when he did take a piece of worm, he would give it a good shake before he ate it, sort of like a dog lol.

Thanks for your replies.