Certainly humidity is not our problem in central Alberta or central BC. Occasional periods of -40C on the other hand are! As I am sure you well know, having spent time over here. Heated storage doesn't need to be all that heated though: keeping the temperature around the 4C mark is very effective and does not cost that much, really never more than a dollar or two a day in the coldest spells.
Qualicum would be very nice and mild, plus not too wet. Although Port Alice was beautiful, 120 inches of rain annually does not appeal, since I lived in Wales and western Oregon, with close to 50 inches a year and frankly that was too wet for me. Sailing in that northwest corner of Vancouver Island should be very pleasant though. As you say, there is wonderful coastal sailing in that area, equaling the Baltic and Scandinavia.
Stuart Lake is astonishingly beautiful. I keep on meeting people who were driving through the area 20 or 40 years ago and simply stayed. Population density is low, and 90% of the lakeshore is undeveloped, being forestry land or First Nations land. There is a shortage of facilities for boaters, I think this is because most locals have their own dock or mooring, but you are right, Cottonwood Marina is the place to launch. This is where our Seaward is docked for the season, at very reasonable rates, with a full time marina attendant living at the entrance to the marina. Pump out tank is on site, and an adjacent park has free RV dumping and freshwater. Several BC Parks facilities are along the shoreline, with fantastic camping sites, and all necessary amenities are found in the town of Fort St. James.
Stuart Lake itself is some 50 miles long, but there is a navigable river system passing through two more lakes, which enables a boat the size of a Seaward to travel some 180 miles northwestward, or so I am informed.
This area is very historic, in West Coast terms. Even before there was the vast Oregon Territory, in the 18th and early 19th century Fort St. James was the administrative center of New Caledonia, which covered most of present BC and much of Alberta, with access coming from Hudson's Bay and the Great Lakes via what seem to us impossibly long foot and canoe routes across vast swaths of forest and swamp. Those people were tough!. The Hudson's Bay Company was the effective government, and control remained in Fort St. James until the more southern routes were developed in the early 19th century, and control migrated first to the Portland/Columbia/Astoria area and then with the partition of the Oregon Territory along the 45th Parallel between Britain and the US, Canadian control moved to Victoria. The most original and best preserved of all the Hudson's Bay forts is found at Fort St. James. The locals are very proud of it, and carry out historical reenactments throughout the summer months, with the probable exception of this sad year.
This is a view across the lake northwestward at dusk on our last visit, with the Skeena mountains deep in the distance:
This is the view from our lake lot northwards towards Mount Pope, which abuts the lake:
This is a partial view, looking eastward, of Fort St. James, with the oldest church in BC still in good condition. The marina is located in line with the church:
And finally a view of Cottonwood Marina. Our Seaward is out of the picture on the left:
Well, that might be more than you asked me for!