Priming just a few bottles with DME

I want to prime 12 bottles using DME. I want to add the DME directly to each bottle.

The plan is to add a different amount to 1/2 the bottles, I can't remember off the top of my head but I read that it should be 1 tsp for each bottle, I want to add 1 tsp to 6 bottles and 1/2 tsp to the other 6. My goal is just to see what will carb better so I don't end up with gushers again when I take a few in for a pro to sample.

My questions are:
Do I need to boil the DME to sanitize it? If so, how much water should I use since I plan to add it directly to each bottle.
Is it teaspoons or tablespoons?

Man, that sounds really complicated. Why don't you just buy some Munton's Carb Tabs and call it good?

Add 3 for light carbonation, 4 for typical, and 5 for high.

I've never used them, but if I was doing partial batches, I would.