Elliot, thanks so much for sharing your story... and congratulations on winning your battle with cancer!!!
Regarding your enormous layout... all I can say is WOW!!! We don't normally see huge double-decker O-Gauge layouts built with the works. Those types of layouts are more commonly done in HO or N scale due to the HUGE amount of real estate that would be required to pull off something equivalent in O-Scale.
Given that you've invested so much time, energy and resources thus far, I'd definitely suggest bringing in more resources to help you if you feel your energy-level would be stressed now. It would be very difficult to scale back at this stage of the game.
I have a few more thoughts/comments to add, but I'll do that later as I'm heading out the door now.
All the best, Elliot.
David