Madara had a rinnegan at that point and is an Uchiha, I think that's the difference betwenn them two.
Madara has the genes, Kakashi does not.
No, Obito will leave him and he will be a fodder again.
Madara has the genes, Kakashi does not.
Madara could use susano despite of being blind, what makes you think kakashi needs MS to use Susano ?