Bonjour Hans,
Great progress indeed, bravo !
Based on my experience with these little engines (I have made a Playlist for this topic :
https://www.youtube.com/watch?v=Q91Ju0Peu2Q&list=PLCVcZL8L7sBJ-ILRmMDuBQk9Jz-aOd-AE&pp=gAQB) they are AWFULLY difficult to adjust.
I work by trial and error on only a few degrees forward or backward for every new test as the temperature of the room is never the same.
Furthermore, I noticed that sometimes the mixture air/gas has to be just a little little bit adjusted (closed) when the engine gets warm.
As gasoline, I was suggested Alkylate 2T and it is great advice :