Your barpath looks good to me for raw lifting. It shouldn't go straight up. You're still not squeezing your shoulder blades together and getting up on your traps. This will help you stay tight and decrease your range of motion. Getting a bench belt might help your arch too(even though your arch looks good). I only wear a belt for shirted benching. I don't know if it helps raw bench or not. Really try to remember to hold the bar at the top. Use your spotter and have him give you commands, just like in a meet. He's got nothing to do anyway. Have him handoff, give a "start" command, press and rack commands. It will help you at a meet.
"I can't wait 'til tomorrow, 'cause I get stronger every day!"