I weigh 315lb. I run 28mm tires. 100psi front, 110psi rear. 2500miles this year so far. No pinch flats. I’m sure my rolling resistance is way higher than a 150lb guy, but I can move along between 18-20mph on the flats. Now that’s a tire torture test!
You may not be running into any problems except tire wear is quicker than it should be. Before we get into a tug of war here please see this site:
http://www.dorkypantsr.us/bike-tire-pressure-calculator.html This is a long known idea pressure calculator based on the 15% drop method that has been proven time and time again over the last at least 40 years and is still recommended today. If you go to the second calculator and enter your weight including wearing your cycling kit PLUS your bike's weight including water bottles you'll find something interesting which I'll address in a bit. For example, you said you weigh 315 pounds, I'm assuming that's you naked, add say another pound for clothing and shoes, now let's add in your bike weight, I have no ideal what bike you have but let's assume fully loaded and ready to ride it weighs 20 pounds, so 315 plus 1 (not a big deal but should be noted) plus 20 equals 336 so enter that number in the first box that says Rider + Bike. Next the second box that says F/R Weight distribution leave at 40/60 if you have a typical road bike. Next enter in your tire size front and rear which you said was 28mm. When you enter the tire size the calculator automatically will provide the PSI level you should be at with in 5 PSI plus or minus depending on rider preference toward comfort or speed.
Here's the interesting part I promised I would discuss. Note the recommended psi, the front is 101 psi so your current 100 is fine for you and your 28mm tires your using. However the rear is not fine, note for the rear it says 154 psi, I guarantee you that your rear tire will not allow you to put that much air into it. So what does this mean if your running over 30 pounds less than you should? You did answer that by mentioning rolling resistance, so that is one issue; the other issue which I'm surprise you haven't encountered is snake bites but you might be riding on really good roads so that may not be an issue; but in addition to low of PSI in a tire will allow the tire to pick up more road debris increasing your chances of a flat because you are riding partially on the sidewall of the tire and most flat protection belts are only on the tread and not the sidewall, and the rear by nature of its position is more prone to flats anyways so you need to find ways to reduce those chances and not increase it; also you will suffer from decrease handling, and increase and uneven tire wear with the fastest were happening on the sides instead of down the middle.
For wet road conditions your tires will have better wet handling response by lowering the pressure all around by about 10 psi in the front and 12 in the rear.
So now you're screaming at me, sorry. But there is a simple solution, go back to the tire calculator and put in a 32mm tire for the rear and see what happens...BOOM...suddenly it's only 119 psi, which should be close to the max PSI on the sidewall. Another option, if riding comfort is your priority you could go with 32's all the way around which of course means lower front psi which will reduce road vibration, but a lot of road bikes won't accept a 32 on the front so you have to check your bike. Having mentioned what a bike may or may not take in tire size it's also highly possible you can't put a 32 on the rear either, so now what? Some tires are rated for heavier riders, tires like the Conti Gatorskin Hardshell, Panaracer Pasela, Specialized All Condition Armadillo, or All Condition Armadillo Elite, and Bontrager Race Lite Hardcase, there may be some others out there as well but I that's all I can think of right now. Anyways that list of tires you can use in a 28c but you would have to use the max psi on the rear that's listed on the sidewall. Also using a bit thicker tube, meaning not a racing tube, but a cheaper tube, will help with keeping the sidewall a tad stiffer.
Please note; this is only my opinion, what you do is up to you, but to have the best handling, flat protection, and wear you should seriously consider making some changes, if none of that is important to you then just keep on keeping on.
