Hello friends! I contacted the team about the first issue and have some details. Interestingly, the Palmyran Trade Ships are actually working as intended, though perhaps not in the way you’d expect. Let me explain:
The amount of gold that is collected by a Trade Ship is calculated by the distance it has to travel between the two docks. At a minimum distance—when the docks are essentially right next to each other—the ships will receive 7 gold. That amount then scales based on the distance traveled, up to a maximum of 75 gold for longer trips. This is a universal scale and a universal cap for all civilizations.
In regards to the Palmyrans, they begin to receive double the amount of gold as soon as the distance traveled starts scaling beyond the minimum value (of 7 gold). This means that it takes half the distance to reach the maximum payout of 75 gold than any other civilization, though the total amount they can receive from any given trade is still capped at that total.
It can be a bit confusing, but the Palmyrans are properly receiving double the amount up to the maximum amount allowed for Trade Ships. It can also be noted that this is consistent with the original behavior in Age of Empires: Rise of Rome.
Hopefully this helps explain the issue! Happy trading!