In terms of movement the port works the same as AAP, its not a new zone.
Under these rules the only way to get them out of port forcibly is by “dislodgement” by taking the territory by land, the naval units are put out to sea which will cause a naval battle on the following turn if enemy ships are blockading.
Also, i would limit air attacks at one round, with AA providing flak fire if present in the territory.
So under these rules the only time a port would be under attack is if you have like a single ship defending or overwhelming odds by air power knowing these planes will be loses