Hi Barbara. We don't recommend using thawed, frozen tomatoes in salsa recipes for canning. The quality of the salsa will not be as good. Mainly, the thawed, frozen tomatoes will be drier. You can certainly cut this recipe in half or quarter it. To avoid having to heat up a large boiling water canner for a small batch, you can make a smaller one of your own with a tall stock pot. I keep a small 12-quart stock pot on hand to make jams and jellies - it never boils over! This is perfect for pint jars of fruit or salsa, too - lots of room for that 1 to 2 inches of water needed to cover all the jars during processing. For the metal tray to keep the jars from touching the bottom, I use the one that came with my pressure cooker. If you don't have one, you can make your own by making a trivet from canning jar screw bands held together with twisty-ties.
Another option, is to make your salsa and freeze it as your storage option.