Who says Eric needs to fight a losing battle (he's not Bill, mmmkay)? He's already exacted the level of direct revenge one could hope for in his situation. If Eric can flee quickly, he can contact the "authority" for sanctuary. The amount of dirt Russell granted Eric access to is more than enough to warrant revocation of the former's lands and title (possibly even execution). Holding "two" states, being old, and controlling a pack of werewolves are quite inadequate if his actions prove unpopular. Given the general distaste of werewolves among vampires, Russell is unlikely to garner support for his cause, once said information is made public to vamps (shouldn't be hard to verify thanks to the aggressive assault, which left witnesses, on the Stackhouse home and the conflicting packs of wolves in Jackson). That is, challenging the "authority" and starting a civil war may have been workable only if Russell didn't "ally" with werewolves. As things stand (with knowledgeable traitors in his camp), Russell's boned and the "authority's" position will solidify once Russell is squelched (yes, ironic).