The 1% and 99% outside design temps in Wilmington NC are +27F and 91F, respectively.  With a 70F heating indoor temp that's a 33F delta, and with a 72F cooling indoor temp that's an 19F delta, which is typical for a zone 3A kind of climate. 

It's really the solar gain that makes all the difference in peak cooling load, not wall R, and in particular the solar gains that come late in the day when outdoor temps are near their peak.  Since you have designed-out west facing glass that has fairly large effects on peak cooling loads for those rooms/zones.  Typical code min builds will have an average load on the order of a ton per 1000 feet of conditioned space, but that's tweakable in the house design.   So if it were just a code min house with average glazing distribution/orientation you'd be looking at something on the order of a 5000-6000 BTU/hr of cooling for that 450 square foot zone, plus the peak heat inputs from plug loads, cooking, etc. (Hopefully you're not roasting turkeys & boiling potatoes with the lid off when it's 91F outside :-) )  With solar gains limited and with a mass wall you should be able to knock that back 1000-1500 BTU/hr, call it 4000 BTU/hr + intermittent cooking spikes + the 24/365 plug loads.

All else being equal the 700' zone would be on the order of 7000 BTU/hr + plug loads, but can probably be reduced to 5000 BTU/hr + plug loads.  The "...huge computer storage array..." needs to be specified in watts to know what it's contribution is to the cooling load (and subtraction from the heating load) really is.  For every 1000 watts it adds another 3412 BTU/hr, so if it's 1500 watts (measure it with a Kill-a-Watt or similar) that would be another ~5000 BTU/hr, bringing it up to the 10,000  BTU/hr range.  (If the power used by the storage array is really that high it would be covering 100% of the heat load for that zone, but it also means that hitting Net Zero could be tough with such a heavy background draw.)

At 90F when the FH09NA is modulating @ 9000 BTU/hr out it's hitting it's super-high 30+ SEER numbers. (That's the modulation level at which it's SEER was rated.)  Running full-out can deliver 12,000 BTU/hr of cooling, but at a somewhat degraded efficiency at output higher than 9000 BTU/hr.  If 12,000 BTU/hr covers the actual design load, the FH09 probably going to be the better choice for that zone than the FH12, due to it's lower minimum modulation.

ERVs help when the outdoor dew points are higher than the indoor dew points, but when it's drier outside than inside it impedes drying a bit.  Either would be fine in your climate.  During the heating season whenever the outdoor temps are 50F or lower an HRV can would usually handle 100% of the dehumidification, without need of mechanical dehumidifiers, unless you're the type to boil food on the stove top all day with the lid off.

While I've contributed to the forum discussions on GBA for a handful of years, blog articles of mine have only been published on that site in just the past month.

Thank you Emmet and Dana!!

Emmet - On which pieces to DIY, and the ICF logistics - thank you - that made some final choices easier. 

Dana- I got my dates mixed up - the article I was referring to was a June 2015: http://www.greenbuildingadvisor.com/articles/dept/musings/how-buy-ductless-minisplit.  Between Holladay, Joe Lstiburek, you, and a few other people, I almost wish I could make a major career change.  So I'm pretty much pulling a "fan girl" moment here - sorry about that.  Serious kudos, though - I would guess that your impact on the carbon footprint has been pretty notable, even just from what people like me here and there have added up in how we do things better. 

Given our nontraditional needs and preferences, basically ending up with wanting a cast-in-place concrete sandwich box, maybe it will be attractive enough for a commercial concrete contractor for the shell.  So I started doing some random digging to see what options are out there, and came up with a couple of ceiling/roof assembly ideas. 

from inside -> outside:
1-concrete waffle slab ceiling--spray or pour polyurethane foam--shotcrete, or thin slab. 

• Can I keep the insulation and crete sandwich roughly continuous? 
  
• It looks like less concrete, great strength, two-way support with a few columns(with more flexibility for placement), and a great support for a hanging ceiling should someone want that later.  Is my perception off here?
  
• I saw that the potential exists for this type of slab ceiling to be relatively inexpensive (compared to other concrete assemblies under certain circumstances) - given likely 2100sf - 2400sf plus the rest of the envelope, how likely is this to be affordable? .
• Could I run small passages (conduit voids during pour, or drilled ) through the waffle beams to support lighting?  Or hang plants, etc.  Also, it looks like an AMAZING way to suspend some of the things I need to have around for my son - like the monitor/speakers, cameras, noisemakers, fans, etc.  It's very difficult to do those things without him being able to reach them really easily when he's having a meltdown. 

2-AAC planks--spray/pour foam--slab.  How would the AAC planks be supported/connected, wouldn't this be REALLY expensive?

3--Holedeck--foam--thin slab

• http://holedeck.com/en/
• This is one of the most amazing looking concepts I've ever seen - practical and beautiful. 
  
• flexibility for mechanicals or finishing later if we ever sold the house
  
• I'd imagine this would be difficult to find a contractor that could do it - or not? 
  

And of course there's the big dream - J and I would love to have a green roof.  With a zen garden, greenhouse, and solar panels among it all. 

So this sounds like what I would LIKE best - holedeck--foam--green.  I'm assuming an EPDM or TPO - there will certainly be bugs.  I know that PU foam isn't the greatest environmental option, but the poured foam option seems like it would be a better seamless barrier and insulator, with less labor.  I know this is kinda like ordering a diet soda with a big mac, but limiting labor cost and risk of infiltration is a big deal, especially since we don't have endless finances.  (although more now that we've cut $3k off the HVAC budget, thank you!!)

Now back to practical reality - anyone have any recommendations on concrete and structural engineers in the central/eastern NC area?