What are the standard guidelines for stock grants to key executives in
a startup?  Quantitative answers required w/ reference-able information.

I don't think that such guidelines exist. It's just a matter of
agreement between the management and the business angels (those who
provided the seed capital).
If you look at public records, you'll see that each company has its
own, unique "stock options plan" or similar. The fact is that there
are too many variables to extrapolate a rule of thumb. Things like
salary, bonus, sales incentives, and so on are very different in every
company, so stock grants, which should complete the employee's (or
executive's) income picture are also variable.

I hope this helps.