I'm having a game crash every time when I kick this one companion out of my clan, he also had his own party and automatically leaves my party to create his own now, I am stuck with this man for life.

Did you try disbanding his party before kicking him? You go in the party menu, select the icon to change the leader and choose disband, he should stop recreating his own party.

I don't know what you did to get stuck like this but really looks like something "Unnatural" in the game, so i wouldn't mind having more information.

The game keep facing a problem when i start the game, it crashes everytime, i've already tried to reinstall the mod but there's still the same problem.

Do you have more information about the crash?
There should be a patch this week about an issue with the auto rebuilt, might be your crash, but wanted to be sure it was the right one.

There is also, currently on the nexus a report where Banner Kings apparently duplicates itemroster elements in town and both the base game and Useful Companions really DOESN'T like this. The vanilla game makes strange behavior but do not crash, but UC instantly crash with this.
So might also be this issue, it's why i need a bit more information to know what to do. (And working on a way to prevent the crash with banner kings even if it's something on their end AGAIN, i spend my time with their issues lately)