I really like this culture setup.
Damn a lot of work to do of course for the events etc, but it looks very nice and promising.
Some insignificant things to:
-Istria should be Venetian or better "Dalmatian" (as a mix of Italians and Slavs)?
-May be it is better to make Danish culture purple? In order not to confuse it with English, especially in the colonies.
-Abkhazia province should be Caucasian.
-Daghestan is also Caucasian.
-Kars should be Armenian.
-Van should be Kurdish.
Also don't forget about Gotland (I would rather make it Swedish simply).
You will also still need to add several religions: East Christianity (Armenia, Lebanon, Ethiopia), Zoroastrianism for East may be. As they are now "pagan".
Regarding some country\provinces:
-Massa should probably be part of Genoa if you are not going to make it separate state.
-Same with Laueburg: better give it to Hanover/Brunswick (at last close dynasties). And remove port here please.
-How is Guelders supposed to work? Are there any events for it to appear after the death of Duke Rainald?
-Teutonic Order capital should be in Warmia (Marienburg) and if the provinces captured by the Poles moved to Prussia. There were some good events in WATK probably.
-There are two capitals in Morocco (kind of fun so
).
-Imereti and Guria should be part of Georgia. Abkhazia is only one province minor. Also remove ports from Abkhazia, Imereti and Kars. Leave only one in Guria.
Regarding cores:
-Probably it has sense to give Poland a claim core of Warmia.
-Teutonic Order should rather have a claim core on Samagotia, not a national one.
-Muscovy should have national cores on Kurks, Voronezh, Vyatka, Velikija, Stolbova and Lukomorje (probably on Ustyug too). Copy these claims for other Russian states as they are the same for all of them to simulate the struggle for the Russian unification.
-Karjala shoudl be part of Novgorod. And Orthodox.
About province capitals names:
-Capital of Karjala should be Kexholm
-I think it is more wise to use Swedish name for Viipuri (Viborg)
-Then also Björneborg for Satakunda
-Capital of Östergötland missing one umlaut: Link
öping
-Capital of Holstein should be Kiel
-Capital of Gelre is Arnhem
-Samogitia: Raseiniai
-Wilna: Vilna (this is ancient universal Baltic, Latin, Ruthenian, Polish, English etc form; better than simple modern Lithuanian Vilnius)
-Podlasie: Drohiczyn
-Mstislav: Mogilev
-Braclav: Braclav
-Zaporozhe: Sich
-Velikija: Velikiye Luki (just a small spelling fix)
I am not sure about all this anachronistic 19th century towns in the Horde lands (Donetsk, Stavropol etc). Probably someone with the better knowledge of the area will fix them.