A couple of key items to remember
-- Flight earning is determined by the flight operator. A UA codeshare designation has no bearing.
-- The operating airline fare class is needed to determine mileage earning. The listed UA codeshare fare class does not provide the needed info. In the class of codeshares you need to contract the flight operator after booking to determine the true fare class.

Reading the AC MP earning table once you have AC's fare class for the UA codeshare flights will give your the needed answers. The segments are handled independently and the AC TATL segment does not fall into the reduced earning for AC North American flights.