How to fit curtain poles so they won't be pulled down by children?
"It's 4.6kg for the curtain + pole" + a hundred pounds of children (or one or more idiot adults). That calls for steel pipe and structural pipe base, preferably threaded and not setscrew, 1" or larger, with long enough masonry screws to embed 1" into the masonry. 

If it's in a 'curtain catalogue', that's not good enough. If it needs to not fall down, then it needs to be able to take me doing pull-ups on it, which is a base prerequisite for anything I mount in a home.

If it's not going to be, then it should be flimsy enough that falling on someone's head won't definitely kill them. If it isn't going to be flimsy, then you'd better mount-the-shit-out-of-it. It basically is a pull-up/grab bar, and some poor sod is going to use it as such eventually.