Tough crack to nut, oh no! I mean this is a tough nut to crack!
It depends on many variables...for example:
-If you dropped out because you had to go to college, now that would be different? Or you would increase your workload? Chances are that you miss two targets with one shot!
-Do you feel that the course is intelectually challenging enough for you? You will learn more things or will drag because other learners in lower levels have the teacher attention? Well, I/we here don´t know.
-Knowledge doesn´t occupy space, the more the merrier, one certificate more could be a difference between get a job, a promotion, or doing some task, depending on to company/department you work with.
And other factors...
Anyway, if you feel like going for it, and getting that certificate, do it. Perhaps you have some time to study, it wouldn´t be a problem for you.
I don´t know for sure, but it seems as though, one way or the other, you are going to study a lot (TOEFL-oriented or if you are back to Fisk) and with Fisk have a permanent certificate, whereas the TOEFL is valid for 2 years. TOEFL is used widely when someone wants to travel, study abroad, etc.
However, withouth much information is hard to suggest something, and even if we do, it´s you that eventually has to weigh the pros and cons of that decision.
I will leave the ball in the experts´ court now.