Answer a) Not a problem as there will be much less tension than a regular tuned 6 string. Because of the shortened scale, you'd need to really loosen off the strings to get it down to E A D G tuning.
Answer B) I'd start with the biggest, thickest strings you can get. If they're too thin, they'll just flap around like over-cooked spaghetti.
I'm thinking a good place to start would be E - 0.130, A - 0.100, D - 0.080, G - 0.065. Basically a 5 string set without the 0.045 G string.