Yes, FASTIDIOUS is a Scrabble word!

Letter values in Scrabble US: F 4, A 1, S 1, T 1, I 1, D 2, I 1, O 1, U 1, S 1.

Is it a valid word?

FASTIDIOUS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

giving careful attention to detail; hard to please; excessively concerned with cleanliness
having complicated nutritional requirements; especially growing only in special artificial cultures