If one converted to a Roth in August and then later recharacterized to the traditional IRA and now finds that the original August conversion date will be most beneficial, is there a way to recharacterize backwards to the original conversion date? Is there a way to just "undo" the recharacterization? (Market timing is tough and made tougher by brokerage firms paper processing delays.)

No. The recharacterization is irrevocable.