Tuning Edelbrock performers

To all the carb techs out there:
I have an Edelbrock 600 cfm performer carb and manifold on a stock 350 in a 5000 lbs Chevy Van.
I know HOW to tune the carb (with all the different calibrations and so on), but I don't exactly know what change will do what. Here are my assumptions, please correct me if I'm wrong:

1. leaner settings will cause the engine to run hotter (richer -> cooler)
2. leaner will save gas to some extent because of the highe AF-ratio
3. richer will cost gas because gas is used to keep temp in the cylinders down
4. I will have to run a cooler thermostat to compensate for lean settings
5. 600 cfm is enough
6. setting lean in cruis and rich in power mode will scramble all settings
7. lean needs less spark advance (rich -> more)
8. lean needs a stronger spark
9. "leaning it out" will get me lower power but better mileage
10. richening it will get better power but worse mileage and emissions
11. I will have to change heat range of my plugs.

Please help me out on this one, I know how it ought to work theoretically, but what I really want to know is what works for heavy daily drivers and what doesn't.
I want the van to be a nicely cruising daily driver and I'm concerned about mileage. I'm not very much concerned about power or tire spins (of course I don't want to cut power out completely;) ). They're fun, but thats nothing for my band's tour van.
HELP !!