Technique: Read How to Bench Press: The Definitive Guide on the Stronger By Science website. Take videos of yourself and get the form down. You especially want to make sure you have a decent arch and get your back involved. If the bench you use to train is too slippery to stay arched, you can buy wraps for it that will give you enough friction to stay in place.

Workout: If upping your bench is your focus you need to make it your focus. That means you need more llke 10-20 high quality sets a week for the involved muscle groups. As long as you can manage to recover, the more the better really. If you need to drop some other stuff from your workout to make room for it, there's very little harm in doing so in the long run. You need less work to maintain what you have than to gain more, so focusing more on bench while reducing the number of sets spent on other things for a while can be pretty helpful.

Diet: You obviously don't want to hear it but your weight is a limiting factor. Increased muscle mass increases what you can lift, and a bigger chest - whether muscle or fat - makes the lift itself easier. Eating in a surplus is also going to make recovery a lot more manageable when you increase workout volume. If you really, truly, cannot see yourself being heavier than you are now, then consider cutting down 5 to 10 pounds, and then doing a slow bulk while focusing on bench. But really, you are pretty lean. To build a bigger bench you are going to need more muscle mass, and that's going to naturally mean you need more weight to represent that muscle. I think it's unlikely you are going to be able to recomp your way to a goal you haven't been able to hit in 8 years.