I have a similar situation with a Turkish flight for Succos. Due to the cancelled second flight from Istanbul, they rescheduled me for a later flight 7 hours after the initial flight is supposed to land. I spoke to an agent and explained there is a flight 70 minutes after the first flight lands. He told me he could change flights, but if I miss the connection and they have to reschedule my second leg from Istambul to Tel Aviv, I would have to pay over $1000 for the change. This is a bit crazy because my return flight after Succos has a 75 minute gap in between flights. The agent explained that if the airline schedules the flight and it is missed they reschedule for free. If you make the change YOU pay.