Don't apologize. This is a gray-area issue that I do not believe has ever been litigated.
1) At this point, can we specify a revocation date of our "S" election that is prior to MAR 16.
A: Yes. You may have missed it in my previous answer. Under 26 CFR §1.1362-6(a)(3)(ii), "If a corporation specifies a date for revocation and the date is expressed in terms of a stated day, month, and year that is on or after the date the revocation is filed, the revocation is effective on and after the date so specified."
2) When is this cancelled debt considered income?
A: COD date is the date when the debt is "charged off" by the creditor.
If your revocation is too late, then the issue falls into the area of nobody knows. Ordinarily, the COD income would be distributed to the S-Corp shareholders IRC §108. However, you have already discharged your personal obligation for the debt, which would have included this COD income had the creditor sought to collect against you directly.
But, now you receive the same income again, indirectly, only through a nonbankruptcy debt to the corporation. There's no precedent for this, as far as I"m aware, which means that a tax court would get to decide, or, you could ask the bankruptcy could to determine the outcome based on an argument that the two debts are really the same, and you've already been discharged. Either way, you suffer serious litigation costs. So, it may be better that if the revocation date is too late, to Chapter 7 the S-Corp and discharge the debt again, because that cost will likely be less than the cost of fighting with the IRS over the treatment of the COD income.