The bar is travelling in a mostly straight line because you don't bring it down very low on your chest. If you bring it down to your sternum, you'll end up with the curved path that you're referring to. If you're actually touching anywhere on your pec, the curve is naturally minimized. Touching lower may become more useful as you start pressing heavier weights.
I mostly pressed like you until I developed pec strains when I got to the point where I was benching in the mid 300's. I eventually had a minor tear, which forced me to change my benching style dramatically. I now touch about 2 inches below my pec to minimize pec strain. I've never felt better.
Have you tried pulling your feet farther back, and maybe just having your toes on the ground? A lot of federations don't require a flat foot bench, so this may help you with arching better. It may feel incredibly uncomfortable at first, but you get used to it. The things you did in you setup did absolutely nothing for your arch.
You maintain adequate tightness throughout the set, so that's good. You don't have happy feet, your arch doesn't change, your ass stays on the bench. A lot of good things, but plenty to improve upon as well. Just keep working at it, you're on the right track!