2006 Jeep Commander - is it okay to run on 7 cyl?

As long as you don’t mind driving a 7 cylinder engine, go right ahead. I’d guess there is more wrong with this engine besides #8 since you should have more power than what you describe.

At some point the #8 may decide to spontaneously destruct itself and lock the engine up solid. At that point you may just have it towed away rather than install a new engine.