At 46, that's a lot of stress on your shoulders. I mean, combined, they are 92 years old! You need recovery time, and it doesn't sound to me like you're getting enough. Maybe cut back on 1 of your workouts, or DON'T go to failure. Leave 1 or 2 reps in the tank, and you will recover faster. As for the post-workout pains, start with ice immediately after; then switch to heat after a few hours. Rotate cold and heat for a couple of days, and that should help. The cold should decrease the inflammation, and the heat will up the bloodflow to the area.
On your form, make sure to keep your shoulder blades pinched together and buried hard into the bench. It puts your shoulder girdle at a less stressful angle.
Check out
this site. And
this site. These guys are IMO the foremost experts on powerlifting. Search through their articles on bench pressing......it'll be a wealth of info.