48 hours, not including shabbos. After that you move on, and you do not need to even tell the shadchan.
I know of a girl who had a situation recently where the boy did not get back to the shadchan for two months.
Assuming a girl asked a shadchan to redt a shidduch to a boy, the boy is under no obligation to get back at all. Usually, the boy is not even told that the girl was behind it. A shidduch begins when the boy says yes.
2 hours
Yes. Whatever.
It is a good idea to not answer in less than 3 days so that you don’t look desperate.
That is ridiculous.