Not sure how AFR would help you remember to dose? Calcium moves slowly and needs to be waaaaay off to cause problems, so I wouldn't worry about dosing too much CaI fit the above, newish, dry rock(Marco) have nothing but issues. I started with 2 part, which ended up being mostly 1 part(ALK) as I rarely had to add calcium and never mag. This is also why I started with A4R, to reduce remembering to dose. I am going to attempt to figure out kalk and try that, probably go the doser route as dealing with the mess of using the ato sounds like a pain and it already has issues with the red Sea ATO
Early tanks have all sorts of processes that consume alkalinity. Early parts of the nitrogen cycle consume it, and processing of nitrate->nitrogen gas or flesh releases it - but the 2nd part isn't happening much in a new tank. Some algae will also use bicarbonate (alkalinity) as a carbon donor for photosynthesis (instead of CO2).
Honestly, dosing is a place I've found it's worth spending some money for dosing pumps (even cheap ones) and timers (or a controller) and just putting the thing on a schedule. Especially if you're dealing with working memory issues/poor executive function/etc. Most controllers can keep track of how much solution is left in your dosing containers, but if not, you can just calculate it out and put a reminder on the calendar.