1. There is a transfer desk, not sure if it's staffed though at that hour?
2. TK normally opens their check-in desks 3 hours before departure at outstations, from my experience.
3. The designated lounge is that of fellow Star Alliance carrier Aegean Airlines. Ignore my comment earlier in this thread where I complained about the Aegean Airlines non-Schengen lounge being "small and overcrowded", as since I wrote that comment a brand new business lounge has been opened, which even ranks among the very best in Europe, in my opinion. Now the issue with it, is that the Aegean Non-Schengen Lounge is only open from 5am until midnight. I'm not sure whether TK has made alternative arrangements with any other lounge for their 03:20 departure, but I'm wondering if there will anyway be a lounge open at that hour. For example, the Goldair non-Schengen lounge is open 7am until 10pm November-March, and only from April to the end of October is open 24/7...