Questions regarding sweetening, carbonation, and other things

Hi everyone, I'm in need of some information for my next batch.

Firstly, sweetening. I do one gallon batches normally, since at the moment 5 gallon brews are not possible. I want to start experimenting with higher specific gravity brews, but I'm not sure how to go about it. Should I dissolve the sugar before adding it to the juice, or dump it right in? Is there a happy medium?

Next, carbonation. I keep producing cider that has little carbonation at the end of primary, and I can't figure out how to make carbonation happen. However, I did recently buy a bag of carbonation tablets at a homebrew supplier, but I wanted to get the community's opinion on using these. Are they good?

I recently got a hydrometer and tested the juice that I normally use for fermentation, and found that it has a specific gravity of 1.049. According to the chart that came with it, that only translates to about 1% potential ABV. However, my brews always seem to be way stronger than that, roughly about the same strength as a strong beer at around 6%. Am I missing something or do I just have an unrefined palate?

And while this final question may merit a post of its own, how do you folks add flavors to your cider? My research always tells me to put in things I want as secondary flavor into secondary fermentation, but I never get positive results. Flavors never seem to come through. It doesn't help that my brews have a weak flavor to begin with, which I also don't entirely understand.

If anyone can offer clarity on any of these questions, I'd appreciate it. I've gone through most of the sidebar resources and experimented a lot, but I never seem to improve my cider beyond a certain point. I generally use safale s-04 yeast and a standard process everytime. Thanks and happy brewing!