4) there are two ways you can do what is called a CrVtec (B20 matted to VTEC head) you can modify the block and the B16 headgasket (harder and not usually practiced) or modify the head and use a CRV head gasket.
On a related note, LsVtec is sort of becoming a pop culture movement..they could call themselves the movement of the dowel pins...

I just made that one up.

5) A fair number to expect from your CrVtec with out too much money or sacraficing streetablilty would be in the 210-220 range, with over 140 lb-feet of torque. I'm not too familiar with forced induction variants, so I'll let someone else field that one.

6) A quick (real basic, not totally acurate) formula to use for drag racing is
100 lbs = 10 horsepower = 1/10th of a second
so to anwser your question, yes 500 lbs makes a huge difference, if you are driving a hatchie thats like 1/4 of your weight, or a teg 1/5th. Are you telling me if you weighed a 25% more tomorrow you wouldn't notice the difference?