Jen,

Since you are taking steps to protect yourself and your baby why not let your husband do the cleaning of the cage on the snake. As far as holding your snake I don't have any facts to give you about any possible hazards to your baby. I'm sure there are others on the forum that can give you that info. Why not just play it safe for the short time. If your husband is holding him/her you can still interact but in a safe way. The time will pass and before you know it you'll be back with your friend.
Is one of your concerns salmonella? Here's a link with some tips in regards to that. Your snakes and their salmonella. Consult with your OBGYN or regular Doctor. Your snake will understand.
I'm not sure what to tell you about handling fish and worm other than standard precautions.
Best of luck and congratulation on your pregnacy.