You've pushed the creation date of the Breadbox PC by a few months, actually
The article was published at the end of Sept last year. Not that it is a big deal...
a) It's not a danger; just a question of possible interference between the PC and radio waves generated by other devices like cell phones, mobile phones. In general, unless you're using one of those types of phones within a few feet, there's no interference I've witnessed. Your al foil idea probably would work fine, but it needs to cover all the case walls.
b) The components will draw no more power than would be found in a normal Morex mini-itx case so it should work fine.