I figured out how I could play this game in Free Play mode. I redraw the map with the smallest map possible and then activate the most fog possible. It draws a lot less detail and my FPS dramatically increases, making this game playable.
I had a HUGE house built from a mountain. OK, so the mountains in small map worlds are tiny, so what. I had four stories up and a basement. The next level down from the basement was a huge cave system that went down five or six other levels. Then, I hit one rock that allowed all this water in, despite plugging it very quickly. Apparently, in free play mode, the water doesn't 'flow' it just appears and there's no way to get rid of it. All levels of the mine caves, the subbasement level and basement were 100% flooded. I was mad. Sure, I can move under water just fine, but it looked lame.
I wanted to save and found I couldn't. I had to buy the game to save. Lame.
Sucks. Sucks big. Sucks big... never mind. Not going to play it anymore, since I can't save. I wanted to keep building, up, but I unplugged my DS3 controller and got the MS blue screen of death.
Fudge puppies! Dude, I was pissed. Lame.
Done.