In terms of the backdating, so to speak.
Waiver is a defence whereby if a company failed to take disciplinary action timeously it is considered that they waived their right to take action.
The test is -
When did the company know about a potential misconduct, and
what did they then do.

As an example - If i discover potential fraud but take 4 months to investigate, that is not a waiver, as, by acting I show an interest in exercising my right.
If I know of a misconduct, do nothing, but after 4 months institute a hearing, this mayconstitute a waiver.

The test of waiver for you, is if the company knew and then failed to act. It brings with it, given your case, the potential argument of tacit acceptance.

As to the Directors duty, while they may be at fault, this is not a defence for you, per se. The question is was there a rule and did you break it.
There is certainly an argument, that when the director paid, it constituted consent.