[Quality Of Life Suggestions]

A few times I have clicked "Break royal ties" by accident (in the kingdom demand/offer menu) - it would be lovely if the answers in those menus are squared in boxes and even better, if keyboard shortcuts are added for navigating the "newsfeed".

[How long does it take to Bolster Culture? (how do you stop the action?)]

"Bolster Culture" works like a "kingdom aura" when activated.
I usually "cast" the aura after conquering a new land until its loayalty goes to 100%.

[Impressions after 42 hours gameplay (normal difficulty)]

There are so many great and interesting things combined in this game, but one has to play it to discover them himself!
I would also like to point some things out similar to your wishlist:
1. You are right about the zoom option - it is especially needed when you start owning a lot of land
2. The "political view" might be touched a bit because with a lot of fights, it gets messy 🙂
3. I think changing knights' skills at the cost of books can also be added, so we can have an extra use of the oversupply of books in the "late game".
4. A super easy setting can be added where knights dont age and die (they remain permanent but at the same time releasable/inprisonable etc.).

[First Impression of a Random Guy]

I was about to write the exact same post but you have already done it 2 months ago...

Cheers! The game is beautiful!