Unfortunately I don't have a Mac, just PC.
Really it's a nice plan and you have a lot of space! My concern with the circular helix is this: if its diameter is 56" and you allow 6.5" (suggested minimum) between turns, that works out to a 3.7% grade. On an O56 curve. Not impossible, but steeper than I would prefer. Depending on train length you might shed a few rubber tires every now and then.
If you could sneak one track width behind the water heater, you could have a separate, oval-shaped helix with a longer run between successive turns. This would reduce the steepness of the grade. Train goes behind the heater, and comes back on the upper level!