If you want to change your primary_culture to something else to form a more potentially attractive union (e.g., Saxon to form Prussia and/or Germany, Dutch to form Netherlands, or Russian to form Russia), it will be far more difficult as SCA than as DAN. You can still do it, but it requires going bankrupt as a OPM (which can be problematic).
Gaining all those newly cored provinces of different cultures changed the math for the culture_gain_threshold (12%) and culture_loss_threshold (5%). Cores and tax values count, so the lone Austrian cored province (I'm guessing you acquired early) was probably already in danger of being lost amidst the Danish and Hannoverian ones and was just overwhelmed by the addition of all the new Norwegian and Swedish ones. Hannoverian might not be 12% anymore, but obviously hasn't dropped below 5%. I suspect the overextension penalty kicked in because you went over the number of provinces you could have before you had to start worrying about it (function of centralization level, IIRC). It's a bit surprising, though, because almost all the new provinces should have been cored, and the cored ratio is the other thing that is relevant for that event (50% you're usually good). So I'm wondering if there is a possibility that you already had the penalty and just noticed it after inheritance?
I suspect forming SCA added enough new cores (e.g., Finnish cores) to bring you back above the required core percentage for your centralization level. Swedish and Norwegian don't get accepted anymore, because you're a union tag (SCA), with a culture within that union, so everything in that culture group is now considered accepted (does not include Finnish, though)
The point is that forming Scandinavia changes your tag and stuff, whereas KoG is just a country modifier just like, well, any other national decision.
Allows you to change your primary culture.
Because Swedish and Norwegian become primary (and thus not accepted) cultures.
I believe you're thinking of the "Create Kingdom of Jerusalem" decision, which is not the same thing.
If your capital province does not have your primary culture, and you have more provinces of your capital's provincial culture than of your national primary culture, you can enact a decision which changes your primary culture to match your capital.
If you are a culture union, all cultures in your culture group are effectively primary.
accepted culture status depends on the tax value of the provinces, not their total income.
They do (or maybe it's calculated based on direct tax, which would work out to basically the same thing).
Since they calculate every month (change triggered on the first of the month, not january) I guess it is not Direct Tax (the yearly tax)
Scandinavia is a cheesy name to look at on the map. They should've made it "Kalmar Union" which sounds cooler.
