The crusts are typical of impetigo - they always comprise yellow exudate that sets into a crumbly large scab with shiny skin beneath.

Definitely they should be washed away with warm water about three times a day, not for cosmetic purposes. It stops it spreading - both in terms of being less appealing to pick at [which spreads the bacteria to the hands] and stopping the bacteria-carrying exudate moving over the skin. Put a bit of calendula tincture in the water to keep it under control - it won't suppress because impetigo is irrepressible by topical non-antibiotic application.

Impetigo is caused either by Staph or Strep infection so it is not surprising that he now has a sore throat - it's the same bacteria casuing it. This is not a good sign because it means the disease is expressing itself at a deeper level. He does need a remedy from your homoeopath at this stage.

The description of his nauseated reaction to being half hot, half cold is typical Stram - that dread of being half dead and half alive.

As for whether he has come through the Stram picture now - is he expressing the fears still or have they been dissolved by Stram? I would say it's likely to be a new remedy picture emerging, and it is a good shift of symptoms to the physical level as you say, but it needs attention.