Don’s reply: Yes, the cabin sole is an integral part of the separate interior liner.The boat doesn't look all that bad.
The cabin sole is an insert (confirm) and not part of the hull. Therefore, freeze crack from water under it is only cosmetic.
However, if it were my boat in your circumstances:
You're just too far away. Even if you fix it up, it will deteriorate again in the same fashion. The amount of work that it needs, none DIY, will be too costly.
Sell it. It's worth several thousand, especially with a good diesel.
Take the money and buy a newer 22-ish footer with an outboard. Easy maint, even tow it home to monitor and do winter tasks.
And enjoy sailing.
If we were still young and at our peak earning years, we could afford the contract labor for maintenance, which is less rigorous in fresh water as opposed to salt water.
The problem with selling it is that the market is pretty thin in Wyoming, where stinkpotters outnumber ragmen by at least 100:1. Also, Buckboard Marina is just a tiny speck on the vast high desert with the nearest community of Green River (pop.12,500 ) some 25 miles away. A further complication is that although Wyoming people are no strangers to the wind and its effects, they are unaware that it can propel boats too.
Downsizing to a 22 footer would be painful for me as my memories of skippering 42 and 46-footers will forever haunt me. That said, we do have two 4WD trucks, both with towing packages. We would have to time the weather carefully, because the Wyoming wind frequently blows over 18-wheelers, sometimes three or more at a time.
If we scrap the boat, I'm wondering if I can convert the 22 HP Yanmar diesel into an emergency standby generator for our home.