That is a glitch but unknown if it will clear by the time of the cruise. If you really want to book shows, cancel your MTD bookings, book the shows and re-book MTD.
The break-even is likely 4-5 drinks per day but that varies a lot depending on the kinds of drinks you'd buy. All of the coffee venues typically use the same beans, and all coffee-based drinks are included, except the ones which include alcohol.
Welcome to CC.
The online planner where you make the purchases (or cancel and re-buy) usually closes about two days before the sailing. You can do this yourself.
No TA talk is allowed on CC.
Welcome to CC.
No, though you may see some on board account charges if you use the same credit card on other folks in the same cabin.
Not much need to link bookings.