a) Yes, share the swap.
b) Ask 5 people you'll get 6 answers
Personally I have a shared swap, boot on hda and just use / for my slackware, I haven't bothered splitting it down. Really I just followed what was written in the Gentoo instructions when I installed that a while back.
On my pc I have on /dev/hda
/boot 32Mb ext2
/ linux 30 odd Mb
And I did have Gentoo on hdb sharing the swap on hda until I toasted it
c) Dunno, but I'd like to know as well .