This game is crazy.whatever you do.they declare wars.teapartys=waste of time=bird stomps=waste of money(and affinity with reign i used 3 my affinity droped from 1.5 to -10) moth princess lost war to the cat princess per one day.i cheated to balance 2 attack 2 def to everyone(doesnt help) to a fair players bit of a choice every playthrough who live our die i guess.
Tea parties - You have to get good events or it can actually make tension worse between kingdoms. The more diplomacy between two kingdoms, the less likely they will declare war on each other. It's not easy but it is possible to get it to the point where they aren't declaring war every 30 mins.
Bird stamps - If you're losing affinity with a kingdom, that's most likely a bug. If anything, their diplomacy with Bird kingdom should just get worst. It's literally supposed to be the alternative to spending affinity to stop a war directly. And the only real way to stop a war involving the Mermaids.
Balance - You played yourself. If you give everyone att/def +2, you only made the fights a coin flip. Instead give everyone max defense, with low attack. Basically just banging on steel walls with sticks.
Affinity - If you have the extra money or hero banner, try and recruit or buy slaves for as many different races as possible. Get their lust to 5 or 6 and spam sex with them to get high affinity. This way if any war starts you can just go to that kingdom's princess/heir and stop the war. Unless they changed it, stopping wars actually builds diplomacy so their less likely to go to war with that same kingdom.