I read through the whole thing and I must admit it was hard to follow even for a long term fan like myself that has played all of the games multiple times. You made some really cool observations that I have never considered before ... Laura and Claudia resemblance and even the idea of thinking of what happened to Laura before and after SH2.

To be honest, I always felt Laura was kind of an odd duck in SH2 as all of the other characters seemed to compliment the story so well. I think you could remove her from the story entirely and not really lose anything meaningful. Perhaps, she represents innocence and the town has nothing to torment her with because she lacks the trauma and a sordid past which all of the other characters possess in ample supply. By contrast to the other characters maybe her presence suggests (considering that she survives the events of SH2 most likely) that tragedies the other characters experienced truly made those people iredeemable.

I would be careful about trying to marry the plot of SH2 to the cult plot of SH origins, SH1, and SH3. I think that stand alone games like SH2 and SH4 worked so well in part because they got away from the evil cult activities which were a big part of SH1 and SH3 especially. The order cult from those games only served (in my eyes) to give a boring and quite generic explanation for the malevolent town. Not all of it was bad ... the burning and torture of Alissa in service of birthing the cult's god was quite disturbing, but it did not deserve further exploration. 

I usually like to take each game as its own separate whole rather than a part of a larger story. Silent Hill works best when there is a focus on a handful of characters and their turmoil. The evil cult stuff is somewhat interesting as a backdrop, but it should really just remain in the background not interfering with the story itself.

The evil of the town does not need to be explained. Horror ceases to be horror when you give an explanation for it ... it is its intelligible nature that makes it so frightening to our rational minds.

The only problem with that analysis is that while Silent Hill did get bigger for SH2, they didn't change a thing about the original town.  The 2nd and 3rd games just take place in a different area of the town that are across Toluca Lake. 

Your theory is interesting, but have you seen a fan-made documentary called "The Real Silent Hill Experience" by Twin Perfect on YouTube? If you haven't seen it, I HIGHLY recomend you (and anybody else reading this) watch it. It's entertaining to watch and might clear up alot of things you ponder about Silent Hill in its entirety. Grab yourself a grape soda, sit back, and exerience:

The documentary is a bit long, but it's shorter than heaven ;)