Two things,
1. The eligibility is only passed after a final determination by an officer. Do you see the officer's note in your GCMS. The link I shared,
https://bit.ly/2RAqmdj, there is a sample note with the officer's review, that is what I am referring to.
2. As regards PoF, IRCC has clarified that it is the exchange rate as on the date of filing your E-APR which will be taken into account and if there is too much fluctuation, the officer will contact the applicant to provide an updated PoF, this was clarified on the twitter handle of IRCC:
A more recent responses given in 2019:
Hope this helps!