<Who decided how many inspectors there would be?

According to this article, it was Blix himself.

When Hans Blix visited the White House last fall to discuss putting U.N. inspectors into Iraq, U.S. officials urged him to double or triple their number. No can do, the Swedish treaty lawyer responded: I can't find enough qualified people and I certainly can't organize that number in a few months.



The idea of tripling the number of inspectors has surfaced again in the desperate search by France and Germany for gimmicks to block the impending American assault on Iraq. But Blix gave the same response to reporters in Athens on Monday. Instant expansion is even more of a non-starter today.



This may also answer your second question, at least in part. Off hand, I don't know the number of inspectors back in the 1990s. At least some of them aren't welcome in Iraq because they were accused of being spied.