The A/C deal as to temperature in the unit is probably a Habitability issue so if you need to do a quick fix and get some window units to cure the problem do that.

We are like outdoor animals at the mercy of the weather. 

Sun 4 seasons great out door activities year round... either way its a personal preference.. and west coast from Vancouver BC to San Deigo is pretty hard to beat compared to the heat and humidity of anything East of the Rockies.For me Napa Valley was the spot I lived there 10 years and I would suffer CA tax's etc to move back in a heart beat..

I can see the following as options:Get rid of the steam boiler and install high-velocity AC/heating (seems like the best, but PRICIEST, option)Limit steam heating to a single unit and install electric baseboard heating on the other two units (perhaps the most cost-effective way to go, though I would still have to install separate AC window units)Limit steam heating to a single unit and install ductless mini-split AC/heaters on the other two unitsRepair/replace the steam boiler with another steam boiler, fix any radiators that have issues, and keep the status quo without zoning heat (not ideal - I can already imagine the third floor being one extreme temperature while the first floor is another)I'm really new to all of this and at a complete loss right now for how to proceed.

Water got in from the gutters and rain hitting the siding face, where it couldn't escape.combined with condensation formed on the inside wall cavity from temperature differences between an air conditioned room at 75 degrees and an outside wall over a 100.  

-Indoor smoker, Outdoor smoker, or nonsmoker?

I have a stairwell that is noisy for one of my units so I will definitely go with some outdoor carpeting to start out and try to dampen that noise. 

And usually, they'll do it in a place like a forest or great outdoor area.

One of the biggest things I would do is sign outdoors, weather permitting (might be difficult if it's raining, with paper documents and all).

I would say that longevity is important and temperature homogeneity.