Campden alone does nothing (other than being an antioxidant). Potassium sorbate and campden together will inhibit yeast reproduction.
Campden will not stop fermentation. But your plan is still viable. Let the cider finish fermenting, and clear to whatever point you want it to. Then sweeten with Stevia/Xylitol and add priming sugar before bottling. I suggest carbonating to 2.4 or 2.5 "volumes of CO2" (that's how they measure carbonation). This calculator will tell you how much priming sugar to add:
http://www.northernbrewer.com/priming-sugar-calculator/
Test a bottle after 2 weeks to see what you have for bubbles. My last batch took a full month to fully carbonate.
Edit: If you're going to force carbonate, then skip the priming sugar. You can rack onto campden and potassium sorbate, wait 3-4 days, then sweeten with whatever you want and carbonate.