I have killed all the saber toothed frogs in our area so I do not have to worry. I have been thinking about doing just what you said with the cinder blocks. I have also looked at ICF insulated concrete forms which I like the best it would just be very labor and time consuming. But that was for the living space. I need a place of safe refuge from a fire because of our location.

As for the clearing of brush the recommended distance is 30 feet is a joke in some area, I think it should be at least 100 feet. This may make your place stand out but it is better having it burn to the ground. One thing on my list is a gas powered pole saw for pruning up the surrounding trees.

One thing I found interesting as well as frightening is houses in the fire zone of the lake fire were burned completely in some case in 15 minutes, that's a hot fire. At one point the fire was burning 1,000 acres per hour! Flaming embers were being blown up to a mile in front of the fire and this was adding to the fire which was also causing its own wind. So part of my education is to plan for the worst and enjoy the best..........