Desperate for answers (Windhoek)

I am desperate to get honest down to earth answers about a life change decision.

I am a black Nigerian that has lived in the UK for over 25 years. I am currently 46 years old. My plan was to move back to Nigeria (I am northerner) in Protected content as we all know, my region of the country is unsafe.

Namibia, Botswana and Zambia according to my research so far are my choice countries to move to - Namibia being on the TOP LIST.

Here are my worries:
I am in an interracial relationship and worried about rumours of racism that I have read about in Namibia.
Are interracial marriages/relationships common and tolerated?
Is it easy to set up a business sucha as restaurant or hair saloon?
Is it easy to obtain a residency visa (I am currently dual citizen of Nigeria & UK).
Where would be the best place to live as an interracial couple (our children are both over 18 now so its just us two).

Many thanks for your help.