I would be much easier to judge how the shoulders fit if you had both hands at your sides. And it would be easier to judge the sleeve length if we could see your full right hand. Maybe you could get someone to take the photo for you.
Based upon your photo, I think the sleeves are too wide in addition to being too long. I would definitely recommend sizing down one. If the shirt is also loose in the chest and stomach, maybe you could even wear a large. The work shirts are more forgiving in this area compared to the westerns.