Masah of the head

Q: When making wudhu, how should the fingers be positioned during masah of the head? I have heard some ulama saying masah of head should be made with all 5 fingers with an open hand, or some say masah of head should be made with 3 fingers (middle ring and baby fingers). Please advise.

Keeping two names

Q:

1) When 2 names are kept, eg Faathimah Zahraa, then is it fine -or not advisable- to call by only one of the names at times. Eg calling the child sometimes by both names, sometimes only faathimah, sometimes zahraa, is this fine?

2) When calling by both names together, would it be pronounced Faathima-tuz-zahraa', or Faathimah zahraa', or would both be fine to say?

Dry blood on the head due to psoriasis

Q:

1) If a person has severe psoriasis of the scalp that bleeds and dries up, then he makes wudhu as normal, but some dry blood remains on his scalp, would the wudhu be valid?

2) If this person touches the blood as his head is bleeding then wipes it on his kurtha by mistake, makes wudhu and performs salaah in that condition where there is some blood on his kurtha, is the salah valid?