Sorry, I didn't have time to have a look at you file. Answering the questions:
1. since this is un-fixed crown, the heir should get the crown anywhere in a settlement if you posses the listed settlement,
2. there's not script in the patch taking away 20k for the crown, so it's not possible ;-) It will be in the next version of the SSHIP
3. I've seen that Mongols are pretty passive but didn't work at all with that.