The best thing to do, like Jhax said, is to run the Quick Setup guide. Understand how the Keymaps, Repeater, Layout and Character sets work, then modify them according to your own needs.

I modified the QuickSetup DPS Keys to where the Keypress 2, has 2 steps, First press broadcasts my totem script, second press of 2, recalls them. And 1 is the "Spam" key, I use almost the exact same script (bunch of /clicks, each calling /castsequence macros).

But i would have never been able to do those without the quick setup wizard and looking through the keymaps, actions and whatnot. Also, sittin in the IS IRC always helps.

As for question 6, you should have no problem, i run the same processor, only 4 Gigs of RAM and a gx260 card, and i don't lag at all.