I would definitely secure HW cloth around the bottom of the coop - YES, chickens, especially if broody, will snug up under there - and being near a treeline especially, other critters might try to sneak in under the radar (and under the coop). Our serama coop is built similarly, and before I got the hw cloth around the bottom, I had a girl "disappear" on me - I just knew a hawk had gotten her - but after a long search, found her broody beneath the new coop! I'm not sure that two blocks would help, since you humans STILL wouldn't really be able to get up under there if a bird or other critter was beneath.
If you've got the cash, then hardware cloth all the way around sounds GREAT!! But a cheaper option is 2x4 welded wire, with hardware cloth just around the bottom 18-24 inches (to prevent reach-ins). It's what I used on our original run (16x36 run...would have cost an arm and a leg to do the entire thing in hw cloth). Raccoons are the most prevalent predator around here, and we've never had one get in with the 2x4 stuff. Of course if you deal with smaller critters such as weasels and such, then maybe you want smaller wire??
I love windows!! Our windows are standard heights, and my birds love looking out them while on their roosts, and they help provide a bit of breeze for them on hot evenings/nights. BUT...we do have ventilation available other than the windows, so our windows are closed in the winter time. Since hubs is obviously handy, you might have him cut two ventilation openings up HIGH on the wall opposite your prevailing winter wind side - cover them with the cheap vent covers from Home Depot/Lowes or just nail hw cloth over them.
It's looking good!!
