Despite numerous searches I can't find a definitive answer to what the carry-on baggage allowance would be in the following scenario:

AA ticket (all sectors are AA flight numbers)

MAN-LHR - BA - 23kg carry-on allowance
LHR-JFK - AA - no weight limit given (Most Significant Carrier)
JFK-LIM - LA - 8kg carry-on allowance

Does IATA Baggage Resolution 302 apply to carry-on baggage limits and therefore the AA allowance would apply to the whole itinerary?

AA website says: "If your connection is on an oneworld alliance airline, and your transatlantic travel is on American Airlines, the American Airlines baggage allowance applies to the entire journey." Does this include carry-on baggage?