When making Ghusl, I know one must make Dua' for whichever Ghusl one is performing, e.g. end of menses or Nifaas. However I have been told that one must fill a bucket with water and make the Dua' and then blow in the bucket of water, after which that water must be used to bathe with, otherwise Ghusl is not completed. This means I cannot make Ghusl in a shower. Is this correct?
Also I have been told that I am not allowed to pray things like Ayah al-Kursi and other Ayahs I have learnt by heart, whilst in the state of impurity from menses or Nifaas. Is this correct? What if one feels afraid or is in pain and seeks comfort from Allah praying these Ayahs? What if one dies in the state of impurity, is one then not allowed to speak the Kalimah?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no particular supplication that should be recited while having a bath after the end of the monthly or confinement period or to remove the state of ritual impurity. Whenever a Muslim needs a ritual bath (Ghusl), he should make intention, wash his/her whole body and run the fingers through his/her hair. Whoever does so, his/her bath is valid.

Blowing in the container of the water after reciting some supplications is not correct. Reciting Ayah al-Kursi or some other verses from the Quran for the purpose of refuge is permissible for an impure person, namely the menstruating woman or the one who is in her confinement period. In addition, according to the preponderant opinion of Muslim scholars, reciting the whole Quran by heart is permissible for a menstruating woman or the one who is in her confinement period. If they avoid reciting Quran for that entire period, most probably they may forget it, which is a great harm.

However, after the bleeding stops they should not recite the Quran until they take the ritual bath.

Know that an impure person may recite supplications just as any normal person.

The person who dies in the state of impurity should be washed in the same way the other dead Muslims are washed.

Reading some verses from Quran or supplications from Ahadeeth to get a cure is permissible.

In brief, only the prayer, the Tawaf around Ka’bah, touching of the Quran, having sex, or reading the Quran after the bleeding stops are forbidden for a menstruating woman. Her bath is valid if she washes all her body with the intention of purity.

Allah knows best.