Just a thought, for a secure dwelling, you might want to consider a shipping cargo container with a high-end padlock or two. A crowbar may be able to defeat it, but I don't know. It would require alot of tools/time to get open, the downside is that it could be locked from the outside when you are on the inside. Of course, you could make an escape hatch on the roof/top, with a ladder. Just throwing that out there. I know that some folks have built HOMES out of cargo containers. They are quite sturdy...and don't burn!
BTW - it really is a sad state of affairs that this discussion has to take place.