Really, don't worry about them, you've got to find out enough about it to be able to make the right decision for you. My answers to your qs below:
What I want to know is what's the norm for talking about a job/finding more about it after you've been offered it
I THINK IT'S FINE TO ASK MORE BY EMAIL OR PHONE
What sort of time frame should I aim for to make a final decision? WHEN YOU FEEL YOU'VE HAD LONG ENOUGH, A FEW DAYS IS STANDARD/OVER A WEEKEND NOT UNUSUAL IME
Is it reasonable to ask to talk to the other person in the organisation who is already in the same job? NOT USUALLY IN MY LINE OF WORK BUT MAY BE USUAL IN ACADEMIA (IS THAT WHERE YOU ARE?)- (so far I have only talked to boss and boss's boss.)
The job description is pretty loose - is it reasonable to ask what specific projects I would be expected to work on in, say, the first year? ABSOLUTELY!!
And can I explicitly ask about the pay grade - obviously I know the salary but I'd like to know what grade it is and how it places me overall in the organisation. OF COURSE
and should I do all this by phone or should I ask to come into the office again? TELL THEM WHAT YOU WANT BY PHONE AND THEY/YOU MAY DECIDE A MEETING IS APPROPRIATE
If I'm really honest my heart isn;t in this job - but it does have certain benefits (a change being one of them) LIST PROS AND CONS, GET THE ANSWERS ABOVE AND ONLY TRY TO DECIDE THEN, ONCE YOU HAVE ALL THE INFO, YOU CAN'T DECIDE UNTIL THEN
Am I in danger of stringing them along if I ask to meet them again? should I just say no and let them get on with offering it to someone else? SO WHAT, DO WHAT'S BEST FOR YOU
HTH