Yes, that's what I do. Crush the tablets and dissolve in some of the cider or a little water, and add that to the cider a day before adding yeast.
Yes, the yeast will start eating the sugar you put in the keg as if you were bottling it. Since you are kegging though it makes your life a lot easier since you're looking for a sweeter cider. You will need to stabilize the cider when it's done fermenting. Follow the instructions in this thread and you should be good to go. Also, I haven't used it yet but many people report that using S-04 to ferment with usually leaves a little bit of sweetness on its own and there's no real need to sweeten. Cheers!I’m just wondering if the sugar is going to activate the yeast again?
If you're keeping the keg cold through its entire life, I wouldn't bother stabilizing it. It may still ferment a little, slowly, but it may not.Is there a full of thumb on rough increments added of sugar to the keg? I’m sure it’s a bit subjective, but I’m not looking for a dry batch. A cup at a time?
Mmm- cider vinegar sounds awesome!!My first cider was done with a very basic procedure, just like beer with champagne yeast and really no additives (I might have thrown a little CS into it). This was in the wayback when the interwebs were devoid of any solid information on anything except beer brewing. It turned out great. I had one batch go sour on me (out of about 3 batches at the time) so I started paying attention to what was available on the net. I got PO'ed at it and left it in the carboy for a year or so in the corner of my garage. I needed the carboy so I dragged it out of hiding and it was covered with a cake of mold. I started to drain it and smelled something good. It made the best apple cider vinegar I have ever tasted and it just kept getting better after a few years, almost 20 years old now and I'm down to less than a gallon These days if I overshoot the apples I keep whatever is left in a plastic gallon jug and forget about it for a couple years.