You're on a roll now! And you're on to something with your back/shoulders.
Driving, weed eating, and all sorts of other stuff makes your shoulders slump. If you're a slumped, you'll probably slump for life. So you need rows and face pulls and pulldowns. Hundreds a week is probably right. The more often you can work back moves into your routine, the better.
Once you've figured out how to use your back work to increase your bench, you have to take that approach to your triceps. 3x10 on dumbbell kickbacks isn't gonna cut it. Aim for hundreds of tricep Pushdowns. Use the cable or bands, and try to avoid skull-crushed moves, to build up volume without killing your elbows. Do dumbbell benches, practice keeping your forearms really vertical. Focus on pushing with the triceps. Learn to get the weight off the front of your shoulders, and onto your triceps.
If you're not a good bench presses naturally, it's hard to improve the bench press by just bench pressing. But its really, really easy to improve on some back and tricep moves. Especially using new hands positions, or just slowing down and "feeling" your reps for a change. Then, you can take these gains to the bench press. Like, how much can I bench with these improved tri's and back muscles?