I have mold - what now?

So I have some sort of stem rot mold on my nothern lights (first grow ever )...or root rot that shows symptoms at the top of the plant.
The inside of my stem is black and moldy looking, the infected branches eventually wither, and dry up.
I looked up images and the closest thing I found was called Stem Cankers but I attached an image.

So my questions:

1. I am in week 6 of my flower (of ~10 weeks for northern lights). Can I cut it down now? Or is the loss from cutting it early so horrible it's better to just wait? I think 1/2 of my plant will live another month. My other plant is totally dead from this T_T
2. Is it safe to turn the buds into butter once they are done?
3. Do I have to do anything to get ready for the next grow? Toss my soil? Clean my tent?
4. I have well drying soil, and airflow. So I don't know how this happened Tips for next time? I was thinking maybe I would get special extra clean shears for my plant and some sort of wound sealer (edit: like pruning paint/tar). Otherwise I have no ideas

I hate to say it but I'd toss the whole thing. Smoking any type of mold or fungal infestation is a bad idea. Definitely not worth letting it go any longer.

Things like this are usually caused by contaminated soil or over watering, and once it's established it spreads through spores. Clean everything thoroughly and toss everything you can't clean, then plant new ones. Really your only option.

Clean the whole room top to bottom. Start washing your hands before touching the plants. Use a fan in the room. Stagnant humid air is ideal for mold growth.