Rather than dictating things you're a little beyond yourself on (I had a ketch; we kept the main on the mainmast, and the mizzen on the mizzen. A second main wouldn't have fit well on the mizzen. In some 20 years of two mast obsession I've seen exactly one schooner with equal masts, and it didn't even have two mainsails!) you might consider seeing what's out there for cheap on craigslist.
A few thousand $ could find you the boat that might fulfil your dreams. Come back here with candidates and the nice folks will help you evaluate. Your initial criteria are pretty good: a head, a galley, a berth. Rules out some tiny pocket cruisers and daysailors. Might add standing headroom, and figure out draft limitations. 5' will do you on the canal systems in Ontario I believe, but I think Mark Twain's riverboats drew less than 2'.
Sorry, not many double masters made in the last 50 years under 35' or so - no need to split the rig. I had one, but it wasn't a comfortable cruising boat