I have replied to your PM.
They should have come with plastic in between them so its easy to seperate them, they should not have sent them to you like that.

You must push and slide[ with your thumb/s, whilst holding the others with your fingers]at the same time to get them apart, you can't just pull them apart.

Some magnet manufacturers say place them south, others say north, i don't think it makes any differance at all, but if it works one way better than the other go for it, but i really don't think it matters at all.
It only matters when you place more than one, creating a strong magnetic field as i explained in my last PM.
Its only when those cards have direct contact with them it may do something to them ,[ say if you rubbed one of your cards with a magnet, well then yes it would] if the cards are in your handbag you shouldn't have any problems.
I have my spare magnets stuck on the side of my PC, the hard drive has a magnet in them anyway, you would have to have a magnet the size of a fist to do anything like your worried about, those ones are very user friendly.
I would not take them off untill about 3 days later, the longer you leave them on the better they work, i only take mine off to bath around the area and put some powder to stop any skin aggravation from the adhesive tape.
Sounds like the one you put one is working good, they have a high gauss reading so you have some good ones.