Sorry for just now respondingas I've been a bit busy. I'm not really the crafting master at all As I only have CRP/CUL 45 Alch 50 and GSM 41~ but I feel I could always just add in a bit more of my opinion ect.

My gear on my Alchemist is 250 INT , ~150 Control ~120 / M Craft : Craft . I'm not looking at them right this minute but its around there. After you posted your ideal skill set up I decided to give perfection another try. On Average on a level 50 Synth (Growth Formula Delta) a Perfection + Byregot's on a Rainbow synth gave me ~115, This is the average taken from about 10 attempts some were as high as 130 while others gave me 96 or so. As opposed to Magnum Opus which gave me ~80 Quality on average on a failed attempt and 200+ on a successful attempt (Sometimes in the 190s) and my success rate was around 50%. Purification gave me about 170-190 Quality on success on a safe color like white. So I'm still a bit skeptical about using Perfection / Culmination; at least on a level 50 Synth. I could try it with some thing with a higher dlvl later but that was just what I found.

Also you can lose up to 12 Durability on a careful synth on a level 54 synth while the element is stable, this has happened to me a lot. Greater Calling is really great for finishing a synth to but from what I hear that if you go unstable it can be quite the nightmare when trying to finish it with Greater Calling as opposed to By the Book (Which I guess if you have enough control your chances of seeing instability should be rare).

Just another side note, when I got my Alch to 50 and it was my only craft to 50 I attempted to make a Growth Formula Delta Concetrate consisting of just one HQ Delta, One NQ and the Lime sulfur. Now I didn't have as many skills as I do now but I could only get up to about 3~4% HQ when I did it, now I did succeed xD but still its a very hard synth. At that same time I had about a 10% HQ chance on the level 50 Delta Growth starting at 0 Quality.