You might want to read the sympathetic lord ruler thread, I think's there's some stuff like that there as well.
I like your theory, but I think it might be the opposite, the lord Ruler released Preservation, and trapped Ruin, for we know that it is Ruin that Vin released from the well, unless that is what you are syaing, and I misunderstood.
On the other thread we were discussing if myabe the Lord Ruler was "preserving," the world in order to prevent chaos, which would strengthen Ruin, meaning that the state of the world affects who is more powerful: Ruin or Preservation. When the Lord Ruler kept things STable, Ruin was weak, but as soon as he died, the world became Chaotic, and Ruin gained power.
Perhaps there is some way to mesh my and your theory together, because I like them bothe so much !
The only hole I can see in this is that, suppposedly, the lord ruler set nothing free, beacuse he took the power instead of giving it away, indicating it is the same entity trapped in the well now as it was then.