I'd say Metema border.
It probably depends on your nationality whether you can get a visa in Khartoum... Probably better to get it beforehand.
Having a visa you can leave the airport at any time. Of course it is in your responsibility to return to the airport on time
Everything is scanned again
Why shouldn't you?
I'd go for KLM (but both aren't great in my eyes)
Ich wechsele immer vor Ort - komplett unproblematisch
Spam würde ich mal sagen
It depends on the airline whether this is a good price or not... Which starting point? Which airline?
I'd say caution Air India lol