1 I can't get clear answer's on the 1080ti wattage. I read 250 watt each, but on load may be more. How much power should they consume if they are undervolted to 70%. Is this safe to run 4x of them on 1x 1000w PSU?

250W is during maximum load so if you run them at 70% we should roughly expect 175W per card. You could get a Wattmeter and keep it in your socket if you want the "true numbers". My say is that is safe to run 4 cards but going higher than 4 you might wanna be careful. Alternatively you could try powering the risers from slave PSU and run 3 gpus on slave and 2 on main.

2 How much power do the risers deliver to the GPU's? The light's and fans continue to run even if the power from the slave PSU is not connected.

I cant answer how much but i definitely think your main PSU. Im curious as to how you are powering the risers, are you using a single cable with multiple sata connectors to power them?

Heres some useful information: https://forum.ethereum.org/discussion/9495/the-correct-way-of-powering-the-risers-for-the-470-480

3 Lastly I'm confused on the "core clock" and "memory clock" on MSI Afterburner. Would adjusting these down help? What setting are ideal?

Clock frequency has little to no impact on power consumption, what matters is the voltage. What settings are ideal are different for each card and since you have mixed brands you basically have to do some trial and error on each card. Core clock seems to have the most impact on mining Lyra2rev2.

Hers a list for comparison where you can see what other 1080 ti's are getting and their settings: http://www.verters.com/vertcoin-hardware-list

Best of luck!