OK, so we have this for the record: this is what I’ve figured out about the rest of the trip. I think I’ve counted the days correctly. In order to apply for the Austrian visa, which allows us 6 months in the Schengen countries, I need to have evidence of a return ticket, so precise arrival and return dates are necessary. We are (I hope) combining here our 6-month Austrian visa with our 90-day EU tourist visa.
3 September 2015: NY-Iceland= 1 Schengen day
4-15 September 2015: London = 12 EU days (out of the 90 we have, e.g. 78 remaining after Visa “D” expires)
15 September-15 March: to Berlin, beginning of Austrian Schengen/National Visa “D”
(In Vienna, 1 October 2015- 5 January 2016)
26 May 2016: LEAVE Europe from Frankfurt for Toronto
5 January-5 February 2016: Lisbon
5 February-7 March: Barcelona/Spain
7 March-5 April 2016: from Barcelona to Athens
5 April 2016: Athens-Zagreb, drive to Dubrovnik
6-25 April 2016: Dubrovnik and environs (Montenegro, etc.)
ca. 25 April-16 May 2016: Trieste
17-23 May 2016: Vienna again
23 May 2016: train to Munich & Frankfurt
26 May 2016: leave Europe via Icelandair from Frankfurt for Toronto
What think?
esauboeck 
It sounds just fantastic. It makes me want to plan a trip for next year. Trip of a life time.
Do it! 🙂