First there is a lot of lying going on about Express Cruisers, the boats that can't get no respect. The "Tug" series of boats, for example, are about as Tuggy as my Rav 4. Show me a genuine tug that can plane. So why call it a tug, because express cruisers aren't cool, but express cruisers they are. Other types of boats are E.C.'s but don't call themselves that, so now we have the "fast" or "swift" trawlers, which are really express cruisers in drag.
First the size of boat. In an article in Pacific Yachting roughly three years ago a woman wrote about what type of boats were suitable for Alaska cruising from southern British Columbia and northern coastal Washington. Her formula was simple, figure out the size you need, then subtract 10 feet. I would say for you a smaller boat single handing it as you get older would be a wiser choice. I suggest you really don't need anything over 30 feet.
The size of your dream. Rather than destinations which will be challenging in terms of distance and fuel, why not compromise with what you will be purchasing and modify the dream to destinations with shorter hops but more frequent. I've recommended this in the past here to others, once you have completed the loop, finishing in Chicago (reason why ahead), you can have your boat trailered across the country to either Washington State or British Columbia. If you trailer the boat, Chicago is a good ending point for the loop and the closest to the west coast, saves trailer fees.
From Washington or southern BC you can run up into Alaska and see incredible scenery, land based wild life, and ocean wild life.
Or you can use this company which isn't cheap, they used to drop off boats in the greater Vancouver area by my place. I would watch boats taken off, then others taken on for transportation.
Canadian Boats and Yachts Shipping - SV Business Group
Type of boat: I suggest either a traditional express cruiser boat along the lines of Cutwater (made on the west coast) or one of the tugs or fast trawler. Sometimes speed is safety. Imagine 60 miles away from home port safety and you have a two hour window to get home before the weather turns nasty. In an express cruiser with some models, you can do that journey in two hours, granted your wallet will be lighter due to fuel costs. But in a traditional trawler at 8 knots, you are looking at 7+ hours.
At one of the trailer companies for boat transportation, their cut off was just a little over 34 feet so a smaller boat will be cheaper and easier to move.
A smaller boat is cheaper in moorage fees, less maintenance bills, less fuel bills, easier to get into guest marinas as you travel. And a smaller boat makes it easier to use. If you get a single engine model, make sure it has or plan on installing a bow thruster.
Also a gas engine in a boat around 30 feet is a good way to go. If it were me with your plans, I'd find a $50,000 older boat in great shape and automatically replace the engine and leg if you get a stern drive. Mercury is now making new engines specifically designed for the marine environment, no longer using marinized auto engines which aren't good for boating for a host of reasons.