For some reason my nordic culture empire lords keep filling up their castles and parties with rhodok troops
It's working fine for me. Maybe just set it once again?
My vassals won't join me in battles or sieges and it seems that they won't garrison troops in their castles in Sword of Damocles.
Well, if they didn't join maybe they were too far. And they do garrison troops in castles. Order them to go to their castle and stay there for some time maybe?
Omg this is impossible!

The invasion has like 60 armys!!!!
And i have like 100 troops with 15 of them dieing after each battle.
Is there some kind of way i could recruit more men?
Thx
PS: I know you can recruit men in tarves talking to the keeper.
And the bandit bribe.
Well. When you create own kingdom you can hire 1 lord for each castle or town. Maximum is 20. First lords are weak but then you get better and better. They are: 5 Knights, 5 Baronets, 4 Barons, 3 Earls and 3 Dukes.
Also you can form patrols of course... Talk to your soldiers and order them to form a patrol, this way you can even have 100 000 army if you have enough money

EDIT:
P.S.
suggestor's suggestions seem convincing

The thing that Taimat396 mentioned also seems interesting. But more discussion is needed i think, and if i add it i think i will make it optional.
Also i would like to hear more opinions about Tactics.