Hey man!
1. Got discord? I'm almost always here so I can help right away.
2. As for a gold mine in Oryeonguk, you discovered a design bug. You see: gold mine adds 100% to the fiefdom's gold yield but Oryeonguk's base yield is 0 (it yields troops), so adding 100% does nothing. I will fix this in 0.3 (coming soon).
3. When you conquer a new fiefdom your army cap increases by 20, thus you can now hold a bigger army and attack stronger fiefdoms.
4. In the old version (0.1) after burning the temple Oryeonguk troops went down to 20 but this was changed in 0.2. Now, after you burn down the temple your troops' effective force is doubled for 20 turns (so you can choose to attack Marbia instead of Oryeonguk). Can you refer me to where you saw that Oryeonguk troops would drop down to 20? I need to fix that.
Version 0.3 is coming in a few weeks. It has shitload of new content, new UI and improved fiefdom management and I believe you'll like it.
Again, you're always welcome to drop by the Discord and chat with us.
Regards,
Doorknob22