Yes, it is permissible to keep on wearing an amulet, talisman, stone, etc. If the verses, Divine Names, or names of Ma'sumeen (a.s.) appear on the outside, then you should avoid touching it. Or, you are able to laminate it, or cover it with clear coloured nail polish, to avoid accidentally touching it.
Yes, you can also read more than seven verses. the only verses you must not read are the verses that have a wajib sajdah.
These verses are in Surah Fussilat, Najm, Sajdah and 'Alaq.
And Allah knows best.