I use regular beer bottles too.
I have powdered sulfite so I'm not sure, but I think campden tablets is 1 tab/gallon crushed. Sorbate is added at 1/2 tsp/gallon. Potassium sorbate is also sold labeled as 'wine stabilizer'.
And yes, rack off the yeast first. I rack into the keg, add sulfite, sorbate, and sugar, then stir and carbonate.