I just finished college and drove a mitsubishi eclipse for the vast majority of my time there. Spent many a night replacing o2 sensors, belts, etc in dorm parking lots, so I feel your pain here.
For such a dramatic loss of power, a cylinder not firing properly would make sense, but you would absolutely 100% without a doubt feel it when you are driving. If it were 3/6 or even 2/6 that weren’t firing, it would (and correct me if I’m wrong here anybody) likely either not run at all, or run so poorly that you wouldn’t be able to drive it period.
In keeping with what the above posts have said, you won’t really get accurate responses until the engine codes are posted on here. They’ll likely try and sell you the “cure” to whatever the engine codes indicate are faulty, and that’s your discretion whether you want to buy it on the spot or come back and let us have a whack at it (this would be my recommendation).
Good luck, and hope to hear back soon.