You are blessed with large feet, but that does suck that it limits your choice of footwear. You may have seen a post from "TheJeff", who is a bigger dude. He raves about various Skechers shoes.
My local running store made the shoe decision very easy for me because they didn't have the Next% in stock, so I didn't get a chance to try it. I did get a fresh pair of Kinvaras, so I've got that going for me.
I've done a little research, and it seems that Nike really does have the market cornered in the light, cushioned, carbon plate marathon shoe department. Everything I've read seems to support the theoretical 4% gain from the Vaporfly series. That's insane! I assumed it was marketing hype and never really gave it much thought till now.
A shoe that provides quicker recovery and faster times is a fantastic development, but until this type of technology becomes ubiquitous, Nike has everyone over a $250 barrel. Hopefully Brooks, New Balance, Saucony, Skechers, etc. will up their game and provide some competition in this market.
As for Chicago, the temps look good, but it is shaping up to be a windy day. If that's the case, I'll try to duck behind someone who matches your description! I'm running from Corral B, Wave 1. I will probably shoot for somewhere around 6:45 pace by my watch and see how it goes. My old watch (Garmin 910XT) was off by about 7 minutes per mile in Detroit, where 6:45 by my watch had me at 6:52 pace according to the course. Of course, if that feels too tough at the beginning, then my plan B is to pass the half in 1:30 and try for 1:29 on the back half.
I have the Stryd footpod now with the Garmin 935, so tunnels, buildings, etc. should not be an issue. The thing is super accurate according to some tests I've done at the local track. Last/only time I raced with it, it was showing that I was running 2 seconds/mile faster than my actual time, so that's an improvement over the old watch, for sure.
Good luck to you!