Your pool is going to be beautiful, I love the idea of moving the tanning ledge to across from the spa. The infringement on the actual surface area of the pool is what took me so long to make a final decision on my pool - I wanted the tanning ledge but I wanted a decent size low end and deep end. You will have the best of both worlds.
Have you thought about keeping the steps to the side so you have true dedicated swim lane, or is that not a necessity? Although I promised we would all be big swimmers when we got the pool, we do everything except swim laps, we play basketball, volleyball, games in the deep end and dive off the jump rock.
You and I are in the same boat being in NJ, we don't get nearly enough time to enjoy the pool, the summer goes so quickly! Having the heater helps for sure, and you have a spa which I sometimes wish I did but was afraid b/c of the weather in NJ it would be better getting a stand alone b/c I could use it all year long. Well, I never did, so no warm water for us!
I love your design, and cant' wait to see it built. What did you decide on for the finish? Plaster, quartz?
It's funny, I never looked at your builder and I am in Berlin Boro, probably should have!

Looks like they are doing a great job and really listen to your concerns.
Good luck and I'll enjoy following your build.