What's the meaning of these slang

1.For ***'s sake, or: Fr heaven's sake, stop that noise. = Bring that noise to an end by all means.
3. I have to take a nap.

I can't help you out with no. 2, 4, and 5.
If I may assume though, no. 4 could mean that something is not safe; the risk of not getting something managed is higher than the possibility of getting it done. - But I'm not sure

I couldn't find #3 or #5, but I've just found this in the dictinary:
to have several irons in the fire: to have various different interests, activities, or plans at the same time.

I didn't know that one!

Miriam

Right, Miriam - that's the correct meaning.
I wonder what I was thinking of - there's certainly a similar saying that fits with the explanation I gave [incorrectly] for no. 4.

When someone is "called on the carpet", they are about to be confronted about a wrong-doing by an authority figure, most commonly a teacher or a boss. The image this phrase brings to mind is of a person standing in the office of a teacher, principal or supervisor -- on the carpet, so to speak -- and being admonished.

"Cash on the barrelhead" is a term of purchase. It is the requirement

The phrase similar to 4. that Pemmican may have had in mind is: "Strike when the iron is hot." It means to take advantage of an opportunity before it's too late.

In blacksmithing, metal is heated until red- or white-hot and then worked with a hammer. Once it cools, it is no longer malleable and can't be worked.

That's it - thanks, dave.

Forty winks . To have a rest . To sleep for a short time
Cash on the nail. Pay instantly.
Had him on the carpet. Reprimanded him.He has too many irons in the fire. He has too many interests.