So sorry to hear all that you and your daughter are going through. I don’t have any answers, but can share what I have found from being on Diamox.
First, CO2 being low is caused by Diamox, but is easily treated with bicarb tablets (I buy them on Amazon). Potassium citrate is for low potassium, which can also happen while on Diamox (it has for me) but as far as I know and have experienced, potassium citrate does not improve the acidity showing us as the low CO2. I have to take bicarb to keep my CO2 in range. Potassium level is a separate test. With both you have to play around with the amount one takes and then run labs to see how much one needs to get in the normal range.
Hope this helps some!