Hawk
Further to the advise above... as you know, the purpose if the FI is to ensure you're ready for OASC; for whatever reason, on this occasion your AFCO thought not. Actually, he's won you some useful thinking and preparation time and the offer to return in just 3 months is positive. Had the AFCO put you forward when not ready, a subsequent potentially weak OASC performance could have been a waste of your CBAT score... remember, you cannot repeat OASC within 12 months.
You should now have a look at what else you've done/you're doing other than ATC: regular physical exercise and some work in the community are quick wins with the latter maybe even providing an opportunity for you to further display your leadership skills.
Thereafter, your next FI will be almost identical to the one you've just taken; think about that carefully and I guarantee you'll be more confident and will deliver a better performance. And finally, given your apparent aptitude it is sensible to include WSOp with an OASC attempt because the Boarding Officers will have the opportunity to take a broader view on your potential. Good luck.