I like your theory and all but I believe it's the way the manga has already told it. The uzumaki's are simply the decendents from the Senju clan.

For one it's not that the Uzamaki couldn't use ninjutsu they just specialize in sealing <-----. There is nothing has been said in the manga the uzumaki's weren't able to use ninjutsu.

For your second point you can't really say he had it or not because it was unclear when he started teaching people ninjutsu. Also the picture you showed looks more the sharigan than the rinnegan to me.

Your last claim is also nonsense when you say he didn't teach people about chakra/ninjutsu when it was clearly stated he did. Chakra itself did not come from the Juubi. All living things have chakra how do you think the Sage was able to weild such weapons.