Watts = v × I × pf
OK, so you have a 200 AMP service panel and if I read correctly the circuit needed to feed the Truck in charge mode is 80 Amps which leaves you 120 Amps at max out to run the rest of your house. I would suspect that since you have 200 you can look at your power bill and see what you run rate is worst case say middle of summer w/AC running etc. The panel if it has space for the breaker to manage the circuit needed to drive the charger head to the truck will more than likely take 2 slots and an electrician will have to run the circuit to point of use as I am sure you know. He/She may suggest a sub panel just for the feed to the charging point. Sort version is if you max at 200 amps and when charging you will have 120 left is that sufficient to run the whole thing and what is the dead to life charge time that you will need to consider. I agree with the formula you used, it all boils down to when you are charging will you have enough to hold it all up. 80 may be a surge number but not knowing the profile of the charger station it is all swag on my part. I had to run a sub panel when adding a 1 1/2 ton A/C unit and beef up my service including the main panel during a construction project adding space to the house. Last that is a lot of juice to pay by the KWH in peak and only get 300 miles but that is your choice.
PMax is dependent on the feed you have from the 12.5 KVA source and your panel is rated only at 200 that is as much as you can push through your system currently unless you upgrade your incoming and the panel to handle the new circuit. Your electric company will be able to look it all over and suggest the best and code acceptable solution for you