Most parkings have height restrictions. The nearest to the theatre Kooldok/Steendok is 2,1m. However, Parking Zuiderterras takes vehicles up to 3,5m (max. length 5m) for 22,6 euro/24 hours. Further afield there is also Parking Rijnkaai. 

 

Parking on the street is not allowed anywhere in the historic city centre. However, the area around the theatre is a red zone, meaning you can park on the street, for max. 3 hours at a rate of 2,30 euro for the 1st hour, +3,4 for the second hour and 5,7 for the 3rd hour and this between 9 and 22hrs. Parking on the street in a red zone is free on Sundays and public holidays (in this case also on Monday). If you want to park further away, in the light green area e.g, same rules apply but it'll be cheaper (1,2euro for 1 hour, 1,6 for the next hours).

 

You can find the Antwerp parking areas here: 

https://www.slimnaarantwerpen.be/nl/auto-taxi/parkeren-straat

 

As for registration, this should be done at the latest the day after entering the LEZ. And as I understand it, it should be instant. You'll find the info here:

https://www.slimnaarantwerpen.be/en/LEZ/registration/overview