Good pointers Andy, stress is one of the much hidden killers

I will add something from experience though, in your "rumors of layoffs" examples you say "companies usually lay off the bottom tier of employees first". Well usually they do, in one role I found my self being in the unusal category when the company decided that the network admin and a developer could do the DBA job.

The best part was about 4 months after being laid off when they me asked back to do some DBA consulting/cleanup work. Their database backups had been failing for weeks and no-one had done anything about it and they consequently lost a pile of data. After sucking them dry for a week or two I knocked back their offer of my old job back

On becoming a contractor/consultant rather than an employee to reduce stress. Well I suppose that really depends on how you feel about contracting and what sort of contracts you get. If you're only getting short 3 month contracts, then I'd say you're more likely to be adding to your stress. On the other hand if you get a nice long 12 month contract, well need I say more ... $$$ ...