To echo, preexhausting the shoulders and triceps is the worst possible thing you could do if you're looking to increase pec involvement in the bench. Those are the weak links in the first place due to the shear mass and mechanical advantage the pecs possess within the movement, so all that does is weaken the weak link further and cause failure at a point where the pecs are getting even less out of the lift.
IME, poor setup is the likely culprit. The pecs will be inhibited by a weak upper back/lats, so first get them tight in your setup, and drill those groups with accessory work. Maximal pec activation occurs in a slight decline, which you just so happen to achieve when in a slight arch with tight traps and lats, and the shoulderblades anchored together and down.
As for the movement itself, try to meet the bar with your chest as you descend. This will cue your upper back to stay tight and put your elbows where they need to be naturally...tucking the elbows aggressively will hurt your bench and is a lazy cue that doesn't address the real issue of upper back tightness. Pause the bar on your chest. Dive bombing is ego BS and will reinforce a loose back. Lastly, squeeze the damn bar and get your knuckles pointed up. Most everyone has wrist drop, which makes for inefficient force transfer through the bar and overloads the triceps, which will cause failure there long before the pecs are properly fatigued. This is why you see people go to false grip benching because it's one less thing to think about. But ultimately you'll be better off learning how to bench without limp wrists
Also, use a moderate to narrow grip...maybe a thumb out from the smooth part of the bar to start out. This increases range of motion and allows for greater contraction at lockout. It does work the triceps more, but it also has been shown over and over again to elicit greater pec activation as well.
The bench press has the best potential for pec development. It's s compound exercise that allows for huge loads and thus maximal muscle activation, while also having great potential for ROM and thus work and muscle tension. Assume your setup is wrong, fix it, and then give bench an honest chance. And db press, do push-ups, and do dips controlled and through a long ROM. If that doesn't get you good chest development then you're screwed anyway.
A 198er with a huge chest who benches 450