Sorry for leaving you hanging last night with so many questions. I was about to fall asleep typing.
Anyway, It has been said that the KH/PH table is not correct relating to C02. You could use it for a reference to see that everything is pretty much stable.
Everyone is either using a Drop Checker which I think you could order from someone on here, Make a DIY one yourself, or do what many people are doing including myself. I do have a drop checker but now I am not using it because I had trouble keeping it on the glass and my regent supply bottle I think went bad because it started staying yellow in the drop checker even after I degassed it.
With DIY C02 on a 45 gallon tank your not going to really keep it stable anyhow and you are probably not going to get it to 30ppm either. Your going to have PH swings do to the fact that it is DIY (yeast).
My KH ranges from 1.12 to 2.8 and I have never had trouble with my fish concerning KH. Unless you have special fish that need a certain KH, I wouldn't worry about it. You need to worry about ammonia, nitrite, & nitrates.
Concerning Co2, what I do and probably most do, is watch the fish, if you see them at the surface gasping for air, your C02 is to high. If your plants are growing well and you don't start having an algae bloom, your C02 is good. You can grow good plants at 10 or 15ppm, but you have less algae problems at 30ppm is the norm for today. I've had my C02 up to 40ppm I know without to much trouble. With DIY C02 you are probably going to end up with maybe 20ppm. If your C02 is stable, your algae will be held at bay. But if your having C02 swings, your algae is going to prosper. Stability is the key.
Its best not to try and catch the dog concerning GH/KH. Try to build your tank around the water type you have and you will not have trouble.
Are you going to dose the E.I. method? Good! Less water tests, saves you money on expensive water test kits. Just change 50% of your water weekly to reset the tank and everything should be just fine.
When I used DIY C02, what I did was have three 2 liter bottles all connected together. I would change one out every week at water change time. This would give me 3 weeks on each bottle. I mixed 1 cup sugar, 1/4 tsp yeast, and filled the bottle to the shoulder with warm (not hot) water. Shake it up real good. For more stability, stand your bottles up in a water bath with a small aquarium heater. This will help keep it steady. Use a bubble counter. You probably would want maybe 2 bps in your size tank. If you get 1 bps, and it is pretty stable, good. Again, stability is the key. If you get purling, great. You might be able to adjust the bubble rate by adjusting the heater slightly. But don't keep adjusting it. Find what works best for you and your tanks. When you can, you might think about pressurized C02. Rex Grigg designs and builds C02 equipment. They are good ones. I bought mine from him about 2 years ago without any trouble at all.
I tried the baking soda for a while and found that it didn't make any difference at all. So now I just leave my KH alone. Everyone seems happy so I am happy.
Check out my tank spec's below in my Blog if you like.
I hope this helps. Read and Read some more on this forum. You will learn a lot. Check out what many has to say. You will see that everyone has different opinions. Its not a very complicated science unless you have complicated fish. Just have fun and enjoy the rewards that come back to you from your efforts in keeping a nice conversation piece in your home.
10 gallon hospital tank.
29 & 50 gallon - High Tech C02 enriched.
50 gallon Pond - Natural.