Don't add the boric acid until you hit target ph and ta, it will make things harder for you.
I'm puzzled too on your fc drop. Did you throw the filters in the tub during the purge then rinse after? Demand is higher than it should be.
Also, I noted you consider using backing soda. I'd avoid it, less is more, practice restraint, sneak up on targets, note your changes when adding so you know what to expect.
Weigh your dichlor, compute your CYA. Chem additions math can be "reversed" to guestimate tub gallons.
On your MA additions, good job!