It's around 4 hours from Pas de la Casa to Barcelona airport. I'm not sure where you've seen a bus leaving Pas at 08:00? There's one at 07:00 and then at 09:00 - the 07:00 bus should arrive at Barcelona airport around 11:00, so should be in good time for your flight.
I am not sure of the transfer time to Barcelona T2, I see there is a transfer at 8.00am from Pas de la Casa, how long will this transfer take? My flight leaves at 13.50. Would this give me enough time? Thank you