It is important to note that potassium metabisulfite is not only a preservative but also a sanitizer. All of your wine should contain potassium metabisulfite for the sake of these two things (aging and sanitation). Potassium metabisulfite is sold typically as what are called campden tablets, and is commonly measured by weight not by volume. It is recommeneded that you use 1 campden tablet per gallon on wine, each tablet weighing .44g (wikipedia) and 10 roughly equal 1 tsp. In a 5 gallon batch you should have theoretically used 1/2 tsp. of the potassium metabisulfite.
Don't think of the potassium metabisulfite as a chemical, but a necessity really. It will not effect the quality of your wine. Allow some time for the wine to sit before bottling after adding the potassium metabisulfite.
The sorbistat-K is for use to prevent renewed fermentation and doesn't have anything to do with any kind of sulfur smells, be careful though if your wine isn't done fermenting when you add the sorbistat-K then try to sweeten your wine you'll be popping corks if you aren't careful.
The sulfur smell definately may have something to do with the potassium metabisulfites, but it is difficult to say, you should've added more... The off smell may have been from the yeast straining, improper sanitation, or something else altogether. It may seem easy to blame the chemicals for this problem, but I would advise you to not give up on them yet. Try it again, use the potassium metabisulfite from the beginning. I would suggest allowing your wine to clear naturally, you don't need sparkloid, just a few weeks or so. Also, (speaking from experience) store your back sweetened bottles upright for a week or so, just in case they decide to pop the corks, I couldn't figure out how my kitchen floor got so sticky until I decided to try a bottle of apple wine...