Some type of defeciency.

[_Maq_]

So you would suggest a test with less than 1 dKH ?

I'm a low-tech, with no experience with CO2 injection. Yet I think that if you get alkalinity that low, you'd have to restrict CO2 injection not to push your pH too low (below 5).
I don't think that would make your plants starving for CO2. Some of my colleagues inject just about 10 mg/L CO2, and their results are pretty good.

For this test i would still use my well water but using HCL to remove the excess KH.

You can try, but with care. I can confirm from my personal experience that lowering pH/alkalinity with strong mineral acid is possible but very very tricky. It takes some time before the pH gets stabilized and you may easily overdose.
A relatively more delicate way is filtration through peat. Even so, you'd have to monitor pH diligently. Peat colours the water but humic acids are generally considered beneficial. Among other things, they chelate micronutrients.