Hey Newbie - to answer the first two of your questions..
1) 5 NA segments with many BOS stopovers are fine. I just booked my itin below with 3 JFK pass so's.
2) Just call the RTW DESK ex.IST (BA IST website) and ask for their email addy.
IST-LHR-SYD-CNS-(stop)-SYD-HKG-JFK-(stop)-CUN-(stop)-JFK-(stop)-AUA-JFK-(stop)-PLS-JFK-(stop)-LHR-ATH-IST
Essentially two big trips and 3 small trips.