1. The reason why trades differ from one broker to the next is as follows:

1- The EA automates MT4 by using trading data to calculate technical indicator levels and act if certain conditions are met.

2- MT4 gets its stream of trading data from the particular broker.

Each broker uses their own individual data stream which differs one from the other. They also have different levels to which they expand the spread during news times. 

In other words, the EA is always the same but the data that it receives to work with from the broker is different from one broker to the next broker and sometimes from one client terminal to another even with the same broker due to Internet congestion, network connectivity and other factors.