It simple he wants sasuke body to decipher the secrete of the rinnegan and last no he can't beat tobi because tobi is not a push over like sasuke, naruto, oro, itachi, kakashi.
to beat tobi you need uge pool of chakra like naruto who can make an army of clone that uses chakra a forbidden technic indeed and knowledge of his crazy technic like phase through and s/t nin. kabuto can't beat tobi and you can say he can summon madara that do, if tobi where to meet the five kage in battle eith his six path jins, i truly believe it would be their death, even though i like the kage's so much but it true,
not even madara could stop him with his crazy technic and mystery and the biju's.
I don't even think naruto can beat him without sasuke help, but sasuke will betray tobi and fight like team seven again on naruto side after the fought. if itachi could have kill him, itachi would have not let naruto have that chance tobi would have been dead already stated tobi.