1. Page 7 Money & Items: "Armor, shields, amulets, and whetstones can only be equipped by one character at a time". So RAW is if a character has an amulet, they are unable to use any of the other items unless they dispose of the amulet?
No, this rule is meant to prevent characters from stacking many of one particular item, like 3 whetstones. Characters can equip one of each of these buff items if they manage to get their hands on them.
2. Page 12 Avoiding a Fight: (minus 3 to attack rolls) This should be -3 to the AC stat and not the die roll? If to the die roll, that would improve the chances and not be disadvantage.
Yes, thank you. My intent is to make it harder, so you should be ADDING 3 to your initial roll when attacking, not subtracting. So when you're trying to roll your AC, you should be adding three to your roll, which is a disadvantage.
3. Page 14 Traps: "If the trap is detected but cannot be disarmed for a narrative reason, then roll to avoid the trap at -3" Again RAW should this not be -3 to your DEX stat and not the die roll to make it more challenging?
This one is accurate as written. My logic is that if a party knows a trap is there, but it's not able to be disarmed due to some reason. Let's say, a pit. You can't really "disarm" a pit. But you know it's there, so I am rewarding the fact that you at least know the trap exists, which makes avoiding it a bit easier. Thus the MINUS three on avoidance roll.
...And now that you mention it, I see another typo on that page. New versions incoming!