Yes; as the word representing the fourth tone on the diatonic musical scale (do, re, mi) fa is an acceptable Scrabble word.
No. Excelsis is not an acceptable Scrabble word.
No. Viz is not an acceptable Scrabble word.
No. Cie is not an acceptable Scrabble word.
Abbreviations are not acceptable in Scrabble.
No. Eariest is not an acceptable Scrabble word.
No. Wop is not an acceptable Scrabble word.
No. Fo is not an acceptable Scrabble word.
Yes. Jo is an acceptable Scrabble word.
Yes. Moot is an acceptable Scrabble word.
Yes. Re is an acceptable Scrabble word.
Yes, "nus" is an acceptable word in Scrabble.
Yes it is Fa is part of the musical scale