Help with first run

[Harmonica dave]

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I made my first run on home built reflux still fired by propane.
Came up to boil at 35 min and stablized at 78-80C degrees, at top of column, and started collecting.
Tossed the heads and got about 1.5 cups of pure. smellt and tasted very clean and burned blue with high acohol content.
It took about 3 hours to get 1.5 cups. This seems very slow.
My mash is sugar based with yeast nutrient.
I had to shut it down and go to sleep planning to start the run again the next day.

The next day i open my still and the mash has a brown tint when it started cloudy clear.
I took out 3 of the 7 scrubbers in column to see if i could reflux less and collect faster.
The scrubers i took out had black residue like soot on them with a burnt sugar smell.
Started to boil again and couldnt keep a constant temp and the collected spirit was slow and smelt way different than first batch.
It wouldnt even light on fire.

Questions: Can you start a run and stop midway and restart the next day. What changed while it sat overnight?
How do i stabalize my temp better? Is the boiler temp going to be different than top column temp? i have thermometer in both. the top reads 78C and boiler reads 100C.
Why did the color of my mash change to brown and have black residue on column packing?
Why is my collection so slow and how do i speed it up to get a gallon of distillate from 5 gallon wash? I was thinking it would take 5 hours or less but its only getting 1.5 cups in 3 hours.

Thank you for your time. I wanna get this right because this hobby has become an obsession that keeps me up at night. Im sure i will have more questions and i will be greatful for the answers.