1: Ok lol
2: It's clear the 7 losses thing was a retcon or was based off him "losing" to Marines so he could raid their ships for food.
I think the idea of having to fight someone who's relative to you in power before fighting another person who seems to be relative to you in power is a very bad idea, since:
One: Kaido would take a long time to beat Shanks, not to mention his whole crew being there while Kaido only had King with him, by the time they finished the war would be over.
Two: Kaido would be too exhausted from fighting Shanks to go to Marineford and fight anyone.
Retreating was the best option.