You're doing everything right.
@Siestarider did some (awesome) testing and found that the vents you're considering are placed at the optimal spot but, if I remember correctly, didn't find any gains re. drag reduction which *might* mean that it wasn't letting more air through the car (although that might have been with the vents that are placed in the center of the hood).
Some people have had good results removing the plastic from the blocked portion of the grill. I'm skeptical that this will help in your case because you've got a stock crash car right behind that part of the grill. Also, every race car builder everywhere is going to say that the opening for your heat exchangers should be about 1/3 the total area of your heat exchangers, so you don't need a bigger hole. If you've having a hard time getting air out of the car a bigger hole to let air in won't make much of an improvement.
It might be time to get racey: pull the bumper cover back off and tape up every nook and cranny with tape (aluminum tape the easiest to work with, in my experience) to ensure that every bit of air has to go through a heat exchanger. There's a spot on the passenger side of the radiator where a tall vertical plastic strip butts up against the radiator and the gap is filled with a piece of foam that loves to fall out, letting air spill off the passenger side of the radiator.
I'd love to hear about your oil temp. If your oil temp. is right at the thermostat temp. then I'd lean towards something being off with the coolant-side of the system. If the oil is hot, too, then the whole system is running hot.