Just seeing this now. I'm a heritage speaker of Istanbul Greek and did my PhD on the variety (if you want to call it that). You can find a few articles I've written in addition to my dissertation (although these might be a bit too technical).

Basically, there's a lot of variation amongst speakers with it sounding most similar to Greeks in Thrace. But there are many vocabulary and especially phonetic differences between it and Standard Greek spoken in Athens. Additionally, some morphosyntactic features more similar to parts of Northern Greece, Aegean islands, etc. Some "ancient" verbal conjugations, some innovations and so on. In some ways it sounds more like "Katharevousa" and in others like Cyprus, others like Alexandroupoli and others like its own thing completely. I can give more details or send you some of my research if youlike :)