In a such tight time I would not drive further north.
Probably you may want to base in Swakopmund/Walvis and enjoy a daytrip until Cape Cross (giant seals colony) and more, if you're keen to drive.
That road is all paved, so theoretically you can drive until Skeleton Park.

Accomodation options tend to be dottd in and around Swapo/Walvis.
Enjoy Namibia, a truly fantastic gem.