However, I am asking if I should take Spring 2014 classes at all.
There are many ways to skin a cat.
I feel like taking classes on the side would push me back to July-Sept MCAT which is already late for the upcoming cycle. I think you can do this as you have to remember, there are juniors (who obviously don't have all their classes done) applying.
I know in relative terms of when to apply (a year before you matriculate), but don't know when as in should I apply for 15 or 16' cycle given that I may need to push MCAT back and take additional classes, IF I need to do that.
If I understand you correctly, you should apply ASAP, whether you have completed the classes and or taken the MCAT or not as I believe you are able to make note on the application that your scores are still coming in. Some schools will pend your application till they see your scores (usually just the MCAT to my understanding).
I don't know if I need to take more classes, when to take the MCAT, etc..
Just take enough classes for you to graduate, in my opinion, and if you got the $, retake some classes. As for MCAT, going with SN2 and taking in May is probs the best plan of action as you can apply and sub your application early with out it having to pend (for the MCAT). If you perform poorly, you still have time to retake the MCAT before 2015 when it changes.