correct tension is vital, but it doesn't mean squat regarding timing. what matters is the tooth count between the timing marks. to confirm this is correct, do both timing marks align /exactly/ for the cam and the crank when the belt is tensioned?
haynes is notoriously CRAP. either get the online stuff from tegger's site or buy the proper workshop manual from helm.
take it to a shop. no disrespect, but all we have to work on at this end is your version of events. if you live close to san francisco, i could look at it for you, but way things are right now, it's impossible to get closer to the problem without physical inspection.