I see. How did you learn about saving in a roguelike? That's another subject I rarely see covered online and a feature I would like to fully implement myself.
I used Monogame's IntermediateSerializer library, which I don't really recommend. Look up game serialization, object serialization, etc. Lots of solutions out there. Your goal is to get all the objects you care about saved into like an XML or binary file that you then load into your game later. It is one of the more annoying things to build yourself, though.
No kidding, I have been struggling with it for a while and it's infuriating that their aren't many good tutorials on them. I will just have to persist till I manage to build something acceptable.
Another thing that immediately caught my attention is how in tilemode your tiles are a different size then your text. How is this exactly possible in sadconsole? In theory it should be breaking the gamewindow.
The game is really multiple console objects, and the dungeon map window is really a "viewport" that limits what the player sees. Each console gets its own font, etc. The way I did it is probably different than the way it's done in the current version, since IIRC there were some big changes between major versions. I recommend reaching out to the SadConsole guys and checking out their documentation and demo projects.