I know I'm not Jay, but I consider myself fairly knowledgeable so I'll try and help.
Tricep sounds like tricep tendonitis, do kneeling push ups for 2 sets of 20 and dumbell kickbacks and tricep pull downs for the same rep/set scheme. You need to treat this like a sprain, so pop anti-inflamms after your workout, maybe look into getting a brace if it doesn't go away, and make sure to ice it EVERY time after you workout. Take a week or 2 off and it should clear itself out, if not go see a doctor because I'm obviously not a medical professional and don't know the WHOLE story, but try that.
For increasing your bench, maybe try a bench specific program(I.E. up your bench 30 lbs in 30 days by WBB) Wannabebig really puts together decent programs that work pretty well, I've heard lots of guys having success with this program(most not the full 30 lbs, but I do know of 3-4 guys who gained the full 30 lbs on their bench). Aside from that, your bench may be stagnating because you've developed tricep pain and can't hit the tris hard enough to make them stronger..and hence increase your bench(only so much chest work you can do, ya know?) Get the tendonitis cleared up and you should be set to get that 3 plate bench.
As for your pecs not squaring out, it could be you just using flat barbell bench as your chest exercise. I know a lot of guys think just flat barbell will give you a big chest(I'm not disagreeing it wont, but it won't be cosmetically appealing). Try doing tricep dips and dumbell bench and pull the dumbells together at the top, this should activate your pectoralis minor and give you a fuller, more cosmetically appealing chest. Tricep dips would work well too, to activate the pecs.
P.S. decline bench is dogshit, don't use it to try and square out your chest, this is what Mark Rippetoes wrote in Starting Strength
"The decline press is a rather useless exercise because the angle of the body in the decline position shortens the distance the bar can travel, decreasing the amount of work done in respect to the distance the load moves. This has the effect of increasing the weight that can be used in the exercise by decreasing its difficulty. This leads to inflated perceptions of one’s ability, and is essentially masturbation, much like that which is possible with a 30 degree leg press or a half-squat. It gets recommended for its effects on the “lower pecs”; dips perform this function much more effectively, which at the same involving more muscle mass, more balance and coordination, and more nervous system activity… Declines are dangerous because if their point of contact on the lower sternum gets missed, the next stop is the throat. Couple this with heavy weight and a lousy spotter, and you might have a really bad “chest” workout."
Hope this helps somewhat. If you need any other stuff answered, I'll try and do my best.
It wouldn't let me quote you for some reason.
