Ok, to answer your question on sorbate. The sorbate makes sterile the yeast, meaning they can't propagate any longer. What yeast is there IS there until they naturally die off. This will prevent fermentation from beginning again in the future.
There are two ways to make a sweeter red wine: 1) The kit was designed this way and one of the last steps is going to add the provided f-pack. In this case, you'll want to add the sorbate as part of the instructions. 2) Let the wine ferment dry, under 1.000 (left alone it will likely get to .990 or somewhere in between). Use the sorbate, to prevent fermentation from occurring again and then back-sweeten to taste. Likely between 1.010 -1.020. You can back-sweeten with a simple syrup that you make. Searching the forum will give you direction.
When I suggested not using the sorbate, it was under the impression that you wanted a dry red. Wine fermented dry (1.000 or less) doesn't need the sorbate. You'll find that most vintners on this site exclude the sorbate for these reasons, 1) Unnecessary, 2) suspected to contribute to the "kit taste" in red wine - #1 being the biggest reason.
I have noticed that kit companies are combining the sorbate and k-meta in one package now. I simply toss that away and add k-meta from my own storage. K-meta (Potassium metabisulfite) is a preservative, which preserves the natural color of wine and protects wine against bacteria.
What other questions do you have?