Why was Arthur there, he too burnt the fields.

Would've saved his life

But then again Arthur also burned the fields

The plot point of the gang robbing the Gray's and Braithwaites' is extremely poorly thought out.

I think that's the point, the entire plan is stupid but Dutch doesn't wanna give up on it, Arthur says a few times that he doesn't think they should do it or that it won't go anywhere.

They killed all the gurads who saw them and flames from that area where the gurads top pritority was the flames he was able to hide in slash near the fields as well not leaving that area unless to shoot a guy and he escaped on horse as well no one followed them cause they were busy with the fire making it harder to reconize him or micha knew that brought him along and some grey mercinary saw sean remedered what he did and killed the poor sap q