Forget about network TV. Your average for the first season of Dollhouse was 3.73 million viewers per episode. Leverage, a huge program for TNT (according to Wikipedia, it’s “ad-supported cable’s #1 entertainment program in the Tuesday 10 p.m. (ET/PT) time slot among viewers, households and adults 25-54”) averages 3.2 million viewers per episode. This thrills TNT.
Because it’s partially supported by subscription fees, cable networks don’t need the super high viewership that you need on network television. (Even better - get a show on Showtime or HBO. You can get away with even lower numbers there.) A good chunk of your viewers probably already have cable, and a percentage of those who don’t will get it just to watch your show. (Bonus - they can DVR Buffy and Angel reruns!)
I assume you’ve already thought of this, but mayve it’s time to approach the cable networks again. You’re once again unemployed at the hands of FOX, I think you’ve got time.