Hi - congrats on your new snake and welcome.

First of all I'd calm down a bit - 10 days is no big deal for a BP and doesn't count as a fast/hunger strike in my book. 5 days is a slightly aggressive feeding regime anyway depending on age.

A BP in shed may or may not feed - mine did when younger but he doesn't now he is an adult - not feeding your snake at all when in blue is a reasonable thing to do.

The white spot sounds like a mite to me - you need to dump the substrate entirely and put him on newspaper/paper towels and treat him as per the caresheets suggest. Newspaper is a great substrate anyway in my opinion.

I'm assuming your BP is a juvenile? What did he eat for you/ his previous owners. My advice would be to leave him alone for a fortnight (no handling except to clean and change water as can't be avoided) and feed him once a week with whatever you gave him before - a rat pup would probably be ideal. If he doesn't eat then take the prey item away and don't feed him again until the next week.

We need more info to really help:
-How old/large is your BP
-What is he housed in
-How are his temps
-What was he fed on before
-Where did you get him.