Hi! Thanks for playing! Happy to help!
1. If you miss, you miss the enemy entirely and deal no damage to the enemy. (The tech skills have a 'push your luck' mechanic, it's hard to succeed at first, but the more skills you learn and/or the more you succeed the luckier you will be when you use them!)
2. I can see the confusion here! You do not include your def stats when taking damage in the fight club. (The idea is that this is not a normal combat situation, and that's the only time DEF is considered) These are expert fighters, and they always strike you in your weak spots. ha!
3. You do not discover the terrain when you have a minor injury. You do move to the new tile, but it stays blank until you move the next day. (You can skip it and move to a new tile in the morning, or explore the blank tile you're on). There is no mechanic to heal the injuries you occur, as a story event triggers after you get 3 of them. That story event only happens once. Otherwise, to heal you'll eat or sleep.
4. When you escape, you move to a different tile and either skip the eating and/or sleeping step for your current day. You spend the next day on the tile you moved to. (So if it's a village, you can heal/shop/etc) You'll stay on the tile you escaped to. (So if it's blank, you'll need to roll for terrains and such. )
Hope these help! Let me know if you have any more questions. I run a discord with a miru specific channel if you want any more direct feedback/faster answers! (I don't see itch notifications immediately, so sorry for any delay!) You can find the link to the discord at hinokodo.com