How much do I make off mods?
Have you been paying attention to Day Z? It's a mod for Arma II, a 2-year-old game - which became so popular, it's pushed Arma II to the top of the Steam best-seller list for months on end. Mods make money by expanding the sales curve, or even bringing an old game back to the best-seller lists years later.
3.6.x has been known for generally being more stable and using less RAM than the modern Firefox 10...
I actually don't agree with your premise. While Firefox had some issues around version 4, Firefox 10 is actually faster and more stable than Firefox 3.6 was, and RAM usage is on a downward trend. I understand that Firefox ~4 turned you off because I was really irritated by the regressions that came around that time, but things *did* get better. If you give it another try and make sure you give it a fair shake without already having decided it's worse, I think you'll find it's actually an improvement over what you're using right now. It's not like Firefox 3.6 was a speed demon in its day either... Firefox's memory hog problems go back way further than that.