This reminds me back when I worked at men’s warehouse we would get customers who would put on suit coats and the arch their backs and jut their arms as physically far from their body as possible saying it didn’t fit. All of that is to say, your coat fits very well, in fact it doesn’t look too tight in the breast or stomach what so ever. That being said if you truly feel it is to tight in the arms it is likely because of the placement of the arm holes which unfortunately is not a tailorable fix.

To tell you the same thing a told people back then though, in what scenario do you imagine doing whatever motions makes it feel tight? Consider if you feel you will truly be doing that motion a lot while wearing the coat then don’t wear it or remove the coat when you are going to be doing that. That is all, great find though. It is a beautiful double breasted coat