I just noticed that you said you were quoted 3900 grafts at one point, Keser doesnt do large procedures he only does small ones, like 1500 to 2000 grafts.
I had a repair hair transplant with Dr Pekiner, my 1st one was a disaster, I went to dr pekiner to try and repair my hair as much as possible, I didn't have a lot of grafts left, I am a diffuse thinner, I only had 1400 grafts and the hairline and the front of my head, he removed some old plugs and also repaired a patchy area in my donor with a 100 graft. I had an FUE, all these doctors perform FUE only, I don't know who does FUT in Turkey but they mostly FUE only and the ABHRS thing doesnt matter, those guys are highly skilled and well trusted, do more research on other forums, Pekiner is famous on the italian forums, if you need more help private message and I will try and help you as much as possible.