More interestingly, how much did Goldberg take off the table in these huge later rounds?

Of course, and it was the execution choices by management that allocated that $300 million in such a way that they didn't arrive at a sustainable business. As such the business goes down the drain and the employees with it.

How much of it was spent on salaries for managers?

If most of the employees are technical, and the company is run like a typical tech company (ie, with too much middle management, but not headcount literally dominated by them), then line employee headcount costs likely dwarf those of management.

That is one reason why executive compensation can get so outrageous; if you have a lot of employees, most singular expenses become rounding errors.

Employees received an average of $1MM over their time there?

Global workforce is/was ~275-300 according to the article.