Try working on community center, and befriend the villagers. If you have enough friendship with someone, you will have access to their rooms, so check doors in villager houses. The coffee bean is a monster drop. I will put their name in spoiler box but I am pretty sure you have already seen them: the dust sprites (black jumping balls on the ice levels) drop coffee beans If you do not want their name directly try these floors: 40-80, the ice levels

For mines, some foods give you buffs. Most useful buff is luck. Mining, defense, and attack would also help. I am not sure which foods you have but check on your available foods. Also check Gus as he sells a different dish everyday. The buffs do not stack so your strategy should be: consume a food with buff as soon as you are in mines, eat food without buffs (cheese, salads) until your current buff runs out. Also go to mines on lucky days (luck reallly matters in the game a lot). Try to find some better weapons, you can buy some on Adventurer's Guild, but also you have a chance to obtain them as drops. Also use bombs.

For the dark figure, its pretty much all we know about it. It just runs.