My opinion would be - don't take the extra class! You already know how stressful 3 was, so don't set yourself up for misery. Don't worry about finishing early; focusing on finishing without burning out from the stress. I never took more than 3 classes at a time because there's no way I could have handled it (and everyone says I'm top of my cohort... ha!)

Is having a review the usual at your school? It's standard to have an annual review for each PhD student in my program every year until candidacy, at which point it's up to the student to arrange it if they want a review - which I did this year to make sure I'm on track for a spring defense. For me, it's actually been a really great thing and one of the things I really value about the program; the fact that the faculty pay that much attention to us is fantastic. Scary at first, but a great opportunity for valuable feedback and planning. For us, the first year review is just a check-up to make sure you're adjusting OK; they start actually expecting something out of us in the second year. And no one expects perfect teaching reviews out of the gate - if that were the case, there would be plenty of jobs to go around because half of the PhDs out there can't really teach to save their lives.

Hang in there - it probably isn't as bad as you're imagining. But make sure not to overload yourself. If you suspect the review is a "bad" thing, then that also suggests that taking on a 4th class is not a great idea, right?