Hi there!
Glad to hear you're enjoying the dungeon generation :-)
To answer your questions:
1. When outnumbered, if a PC is hit by one Enemy, they take extra damage equal to the number of additional Enemies engaged in combat. So to answer your first question, your character takes damage from the Enemy they (partially) failed to attack, plus one extra damage for each of the other Enemies also engaged in combat.
2. If you're fighting multiple Enemies and choose to drink a potion instead of attacking, one Enemy will deal full damage, while the remaining Enemies will deal one extra damage, as explained above. It is up to you to choose (or randomize) which Enemy will deal full damage.
3. With a group of PCs fighting multiple Enemies, it is up to you to choose (or randomize) which Enemy targets which PC that is not attacking.
I hope that helps clarify things! Let me know if you have any more questions.
Thank you for your support!