Scary: slab down yesterday, tomorrow frame will be up

I did a quick google search to see what the time for curing the slab should be and the general consensus (of non-builders) is a minimum of one week. Perhaps you should do a similar thing - I didn't know what type of slab you have (i.e. I have a waffle pod) and that might be a factor in how long they should leave it. Find out how they laid your slab and google that but try to find proper building websites - like your master builders association - and see what the professionals think.

Personally I think putting the frame on now is too soon but, as I said, that's just a personal opinion. Also, you don't want the base stage invoice to be followed by the frame stage invoice the very next day

I don't think it's an issue. I had only 3 days in between my slab and the frame and had it checked out with some experts at the time. As long as you don't have the bricks on it for a couple of weeks, you should be right. The frame is light, and won't stop the rain water either, provided you get some rain of course.