I got a 5 gal batch of cider that's about to be ready to prime and I was curious if it was possible to backsweeten with non-fermentable sweetener like Splenda and prime with dextrose all at the same time in a bottling bucket.
Depends on how sweet you want it. I've used anywhere between 1/2 to 2 cups for 5 gal. It depends on how tart your bevvie is and how sweet you want it to be...
I back sweeten my ciders with splenda. My wife drinks most of them. I usually pull a measured sample and then dissolve some splenda in that sample for her to try. When she says it is good, I then calculate and scale up the amount of splenda for the entire batch. So far this method has worked well.
Lactose (milk sugar) isn't really sweet, it is a sugar, and is largely not fermented by beer yeasts, so will add mouthfeel but not much of a sensation of sweetness. Try (a little) on the tip of your finger and you'll see what I mean.
And as far as adding something like cinnamon flavor would it be best to just steep s couple of sticks in the same water with the priming sugar and Splenda ?
In terms of priming and backsweeting,my last cider I primed with brown sugar and sweetened with Splenda. My wife is very picky when it comes to ciders and wines. So when she said "Its not bad....", I took that as encouragement to make more cider