Is gravity a weak force due to its interaction across other parallel universes... Is dark matter just gravity from other universes acting on ours... Could relativities prediction of infinity at the centre of black holes be explained by the singularity existing in other universes... Could super massive black holes be the cause of galaxies not the big bang...

It goes something like this...

 

In M-theory, gravitons are postulated to be the only bosons whose 'string' is not attached at either end to a brane. That means gravity can 'leak' across branes, and is therefore 'diluted' from its actual strength, which is more in line with the other fundamental forces.

It is because of this 'leakage' that the force of gravity appears, in our brane, to be so many orders of magnitude weaker than the EM force.

 

I don't think string theory is in a position to account for dark matter, as it isn't on solid ground itself.