Can confirm, happened to me on my 1.14.4 server. Side note: it's hilarious.
Could you please attach photos or videos of your options menu, or you trying to type? Also, maybe changing the default T to other key could work?
You should read Witch behavior on https://minecraft.gamepedia.com/Witch
Uploaded .zip world file. Also, I tried playing it with 20w16a and I have no problems, I've been playing it for 2-3 days now. 20w17a didn't gave me the "old world" warning, but 20w16a did.
Can confirm. Tried with empty book and got to page 50 and could go back. Tried writing some gibberish first 4 pages and when I went back it just crashed. This is the crash I get:
The game crashed whilst rendering screen
Error: java.lang.StringIndexOutOfBoundsException:
String index out of range: 9
Can confirm, had the exact same crash message.
Neither them, spider jockeys, chicken jokeys, etc. have saddles. This is not a bug.
Can confirm. I think its because of the Hoglin hitbox.
The world is completely valid, since I opened the world with 20w16a and had no problems. I also opened it with 1.15.2, 1.15.1, 1.14.4, 1.14, 1.13.2, and below and had no issues.