How to Improve Thoracic Mobility for Better Bench Arch

I am trying to improve my bench press arch so I can reduce the range of motion and get more leverage. My lower back is fairly flexible but my thoracic spine feels like a block of wood. I have trouble getting that nice high chest position when I am on the bench.

I have been using a foam roller and doing some thoracic extensions but I am not seeing much progress. Are there any specific stretches or drills that you found particularly effective for opening up the upper back? I want to be able to stay tight and keep my shoulders tucked throughout the entire movement.

Does a better arch actually lead to a significant increase in the weight you can lift? I see some people with massive arches and I am jealous of how little distance the bar has to travel. I would love some advice on how to safely work on this without straining my back.