Proper hand washing is perfectly fine. I don't think that you have to wash any clothes that he touches. I doubt the food poisoning was from the snake. Most salmonella from reptile case are from handling droppings and then eating or putting your hands in your mouth. Which is just eeeeewww! If you wash you hands after every handle and everytime you do the cage you will be totally fine. Btw crusty pee things= urates. 
Morgan