JO is an acceptable scrabble word. Searching the internet many sites have all the acceptable words for a game of scrabble and JO is repeated on 90% of these websites as being correct.
Abbreviations are not acceptable in Scrabble.
No. Excelsis is not an acceptable Scrabble word.
No. Cie is not an acceptable Scrabble word.
No. Viz is not an acceptable Scrabble word.
No. Wop is not an acceptable Scrabble word.
No. Eariest is not an acceptable Scrabble word.
No. Fo is not an acceptable Scrabble word.
Yes, "nus" is an acceptable word in Scrabble.
Yes. Moot is an acceptable Scrabble word.
Yes. Re is an acceptable Scrabble word.
In my eyes yes RN is an acceptable scrabble word.