Correct. The seniors must be gone before capital can be raised, whether written down/extinguished or converted to commons. Both of these add $193B to both core (tier 1) and CET1 capital, which currently stand at -$167B and -$200B respectively.
Yes, I expect the SPSPA amendment to get rid of the seniors once and for all, though perhaps the original $1B liquidation preference could stay because I believe the funding commitment (which needs to stick around per the presidential memo) is tied to the seniors. The 10% dividend won't matter any more once the seniors are gone, though.
The warrants are not tied to the seniors other than that both were issued in the original SPSPAs.
FnF's "repayment" of the seniors plus 10% has nothing whatsoever to do with the warrants. Tying the two together is a very prominent bit of common nonsense.
The idea of the warrants being collateral fails anyway, because if FnF were in enough trouble that they couldn't repay the seniors, the commons (and thus the warrants) wouldn't be worth anything. The warrants are not and were never intended to be collateral.