Where did you do your last 2 semesters? Were they at a 'tougher' university?
I think you need at least 3 semesters in grad school before you can apply as the grad cohort? So you would only be able to apply as the grad cohort for F2017 entry (correct me if I am wrong).
In the meantime you would theoretically be applying with the undergrad cohort for F2016 entry - unless you don't want to use up one of your 4 applications.
So if you do decide to go to grad school and applying with the grad cohort does not work out, you will be able to do a non-degree semester during Fall2017 while applying for Fall 2018 entry. Theoretically if you were to do this, I would potentially advise either going to an 'easy' University for a higher chance at getting a 90+ average or truly going insane with your studies at whatever University and going for that 90+.
Alternatively, if you do not go to grad school, and do one more non-degree semester (Fall2015, assuming you are not past the deadline to apply as a non-degree student) you will be able to apply for F2016 entry. Assuming your last semester had an ~85 average and you are able to get a ~90+ average during this coming Fall2015 semester you would be floating around ~88% for prereqs + last 2 semesters.
Is there any possibility of you taking the Masters acceptance but starting in WINTER2016 instead of Fall 2015? If yes, you could do a non-degree for Fall2015, while applying for Fall2016 OVC entry. In the meantime you would plan to do your grad semesters(Winter2016,Summer2016, Fall2016) and being able to apply for the grad cohort for Fall2017 OVC entry. This last scenario assumes there is a grad school Summer 2016 semester, and obviously that you can delay your masters until a Winter2016 start date. If you could somehow do all this ^, that would definitely be ideal.
I think some of that makes cents
I for one tanked the interview this year... Hopefully a non-degree semester +
huge improvement for the interview portion works out for me for next year.