Joule-Electra VZN OTL Users- I Need advice!

Got my VZN 100’s about a week ago and there are things Id like to get advice about.

Variac:

1. When firing up, do you set it a bit lower than the destination voltage of 65v and after warm up adjust to final destination voltage?

2. Voltage reading is different each time when the dial reaches a point that i marked on the Variac dial. Is that normal?
I would mark the point on the dial, say 65v, after the amp worked for a few hours, but the next day the same point on the dial will give me a different voltage reading.

3. I get +- 3 volts of fluctuation throughout the day. Is that normal? Sometimes i get both blocks to read almost the same, then 30 minutes later one went down 2 volts and the other went up about 2 volts.

4. When aiming for 65v, should the higher of the pair be at 65v or should i get an average of 65v (i.e L-67v/R-63v for example)?

5. For some reason the Bias is not necessarily corresponding to the voltage reading.
In other words, say i biased the tubes to be at 28 when the amp voltage is at 65.
The next day, or after few hours, the same 65v reading gets a different bias reading, as if the tubes fluctuate even in reference to the same voltage within hours- not days/weeks/months.
Its as if i have to rebias all the time. It don’t make sense...

Power cycles:

1. Is it safer/better to shut the Variac off if im not listening for aprox 4-5 hours?

2. Is it Safe/Better to lower the voltage, but not shut off when i go out for an hour or not listening for an hour to a few hours?
It seems like it might make more sense to lower the voltage with the Variac than completely shout off, but i am wondering if it might damage the amp to sit idle at lower voltage than it expects (without playing music).

Tube rolling:

Whats your experience in rolling for the driver and input tubes? Not talking about the output tubes.

Thats my questions for now. Please feel free to add whatever your experience with these unique beasts taught you.

Thanks
Rea