Good work Captain. Don't cut off the stalk- that is your ticket to a plant and flowers. Just plant, place your stake or support and gently cover the shoot. Or if you leave some leaves exposed, protect it from slugs. As it grows, you can fill in the hole all the way.

I would work the soil deeper than 6" though. I like a nice soft, well-worked place for tubers to form below the 6" tuber depth of the original.

Sounds like you're on your way. Congratulations.

This is common question and many people have tubers that have long sprouts on them. According to Phil Mingus(only 60 years experience growing dahlias), if the sprout is longer than an inch or so and there is another smaller sprout, remove the long sprout and let the smaller one grow the new stalk. Long sprouts are skinny and do not thrive. However if it is the only one, you may have to plant it with the long sprout. I have planted tubers with 12 inch long sprouts and the resulting plants were not very good. I was trying to get more tuber production but even though there were a few more tubers, it was not worth it.

If a sprout gets broken off will a new one form? I have some with longish sprouts and it new ones will form and I still have 2 weeks at least before I put them in the ground I was thinking about breaking them off to get new sprouts and a sturdier plant. I have a few plants that are potted up but can't do all of them. The nonpotted up tubers are going crazy.

I cut a sprout off to start a new plant by potting up the sprout. This resulted in four eyes where there had been one.
You can pinch them back, resulting in a shorter plant for now. The plant will concentrate on developing laterals in the next few weeks as opposed to just growing taller. Plus, this will ensure a bushier plant for the season.