Webdev,
I admire your dedication and I think you are going to be fine. Like you said it takes time. PPC takes a lot of testing, trial, etc. but if you keep it up you'll eventually find a profitable niche. I've never heard of anyone getting it right on the first, second or even third try. I was always just too impatient to keep at PPC so I admire your never-give-up attitude.
Hang in there. I'll be reading about your success story soon.