Hey, thanks for playing my game, and an extra thanks for telling me about it!
1. Running back to the Bonfire is completely unrestricted. You can do it as much as you want. This means, just like the in the video games it's inspired by, a player is free to farm the first zone and over-level themselves. However, it gets more and more expensive to level up the more you do it (three times your current level) and enemies in later Realms drop more Souls per Encounter. Ideally, a player gets bored/impatient with the weak stuff and moves forward, but when that happens is up to the player. Some players want a safer experience than others.
2. Brutal is meant to trigger when the Hollow has zero successful or tied matchups in a round. Leftover Hollow's dice that don't find pairs are effectively discarded.
3. The intention with Volatile is that rerolls allow the damage to be avoided. The Hollow decides in which order the conflicting dice pairs resolve (p3), but the rules aren't clear about when non-dice things resolve. Thanks for mentioning this, I'll try to update the rules for greater clarity.
4. The Lost Soul and Hidden Cache secrets work as you interpret them: you can gather up to RN+1 of that thing over the course of several Bonfire resets. I wrote it this way to emulate hidden drops that scale up as you reach tougher areas in Dark Souls, and to pepper the gameplay with several rewards over try-die-repeat attempts rather than a one-time lump sum and then an empty Encounter after. An alternate rule, "you find [RN] Souls/Items (does not reset)" might vibe better with some players, but I haven't tested the idea yet. I'm also working on a supplement that introduces more impactful, found-once-only items, which might scratch that itch. That should come out later this month.
Once again, thanks! Feedback means a lot to me, and I'm always happy to answer questions.