1. Uncertain, but there's a chance? Once they're fully darkened they're pretty much blank slates that do whatever Black says. They would be dangerous to approach and nearly impossible to contain so Garnold and Clukr haven't been able to do any tests with them. It's not out of the question, but it's very unlikely.
2. The darkness won't spread unless the inflicted Sprunki is almost entirely infected, otherwise it can only spread if they are attacked again. A partially infected Sprunki can't spread darkness to an uninfected Sprunki.
I don't mind answering questions! In fact I enjoy it, it gives me a chance to share the lore and random facts I have in my head :)