Dear Clerance,
Seems to be a lot of confusion in his mind; being the dumper, then deciding to be friends (assuming he is the one who wanted to remain friends since you mentioned feeling weird), then blocking for no obvious reasons and without offering you any reason and then resuming contact as if nothing has happened.
NC started to make you feel better; when he told you not to contact him you were able to maintain NC without any discomfort. Unless you wanted to re enter the same cycle again, NC seems your best option. Curiosity is at best allowed to die its own death.