How would you react with a dog eat dog office environment?

I think you have done well to resign your position there. I know I certainly wouldn't want to work at a company that condoned that type of behaviour. Although I suppose it's easier said than done. After all the bills need to be paid. And if you don't have another job quick enough things can be troublesome. Howver in a company like that one is likely to become ill due to the pressure one is under and in the long run that is more precious than, possibly, being out of work for a short time.