I am assuming that this isn't your first shirt so it being tight won't be a total shock.As far as denim goes I don't know. But on my poly Inzer says I should wear between a 58 & 60 and I compete in a 54. The trick is knowing how to put in on correctly so it gets all of the way on so it won't...
I've seen all the west side videos, and read most of the articles on correct form and I still don't keep my tucked in to my sides. It's just not natural for me. I'm not out perpendicular to my body, but I'm pretty damn close. I don't worry too much about it. It's just different strokes for...
The rule on width for most federations is that the rings must be covered with some part of your hand. When I compete I put my index finger on the rings and slide my hands out a little so the skin still covers the rings. ( train with my pinky fingers inside the rings usually)
As far as an arch...
The only time I get weaker by dropping weight is when I do it at the last minute. Once I dropped 8 lbs. in one day and I figure it cost me at least 25lbs on my bench. I don't recommend extreme weight loss, but sometimes ya gotta do what ya gotta do.
If you're stuck, move your grip around ( probably in), change the exercises you do, or change up the reps. Variety is the key, and do not underestimate the importance of your triceps.