Thanks for the tips, I made the correction to the baking soda there.
About the amount, it's two teaspoons, not tablespoons--doh! That also is corrected. I just always used 2-2-2-2 (water, sugar, yeast, and baking powder) because it's easier to remember and tell people. If I was only changing one bottle once a month, I'd worry more about putting too much yeast in there, but each bottle gets changed every two weeks. Hypothetically, I could change one once a month--making the amount of yeast a more important issue--but again it's easier for me to remember to change a bottle at each water change.
Thanks for all your help!