Before you get exited by that still very large number, look at the quality of the assets.
But more importantly, look at the liabilities. I don't see a bank run in there anywhere, unless there is a mad rush to bank currency notes and coin, and the US commercial banks sell billions in notes and specie back to the Fed. As for the $2.7 trillion in bank reserves, that is trapped there until the Fed says otherwise.
Yes the leverage is high, but you can't judge the Fed by the standards of commercial banks. If you are dealing in US dollars, you have to use a US clearing bank, who in turn banks with the US Fed. You don't get to take your business elsewhere.