There's a bunch you need to work on with your bench press.
First is touching your chest. Do you know why you can't? Is is a mobility issue or did you simply not know you weren't touching? I'm hoping it is the latter, because that's easier to fix. If it's mobility, I have zero knowledge so can't really help.
I'd suggest benching the empty bar and seeing if you can touch with that. If you can, add 10 lbs and repeat as many times as possible. Take 90% of the highest load you can touch and use that as your training max.
I'd also suggest working on your setup. From one crappy bencher to another, learning how to get a decent arch makes a massive difference.
Further, bench much, much more often. I think 531 is great, but I've found bench does well when hit with massive amounts of volume. I've found that doing 3x5 at a load I can happily hit with a few reps in the tank every time I train works wonders. Start out with a load that leaves one to two reps in the tank. When it leaves three or more left, add 10 lbs and repeat.
You'll also benefit from getting more mass everywhere (btw you've done well in that respect already) but especially in the upper body and upper back. Rows, rows and rows. Chin ups and pull ups too.
Other than that, keep chipping away and be patient.