Novolin or humulin R don't peak until about 2 hours after injection and lasts about 5 hours. Think about it like a mountain peak. You inject, your working your way up the mountain, it peaks around 2 hours, and the effects go back down the mountain. It's almost a perfect bell shaped mountain.
So how your dosing it the injected insulin is really only coming into play for the meal that occurs 90 min post injection.
If you really wanted to utilize your insulin injections you should do an injection 90 minutes before each meal. If you are exercising pretty hard use a ratio of 1 unit for every 25 carbs...that's higher than what you've heard but its in line with someone who very active...if your counting your carbs right that should also keep you from experiencing significant hypo blood sugars.
So if you eat 80 carbs that's 3.2 u. If you eat 100 carbs that's 4 units. If you eat 50 carbs that's 2 u. Totaling almost 10 units a day, twice what you're taking now...but that would actually be safer than what your doing now.
I would be very careful with how your timing all this with your workouts. Cardio will bring your blood sugar down slowly, heavy weight will spike it for a little bit and then bring it sown very quickly. So if you take an injection 90 minutes before you eat and that's in the middle of your workout, you might be setting yourself up to getting low blood sugars.
Like diesel said, I made it pretty clear how I don't see a benefit to doing all this...but if you are going to do it at least be safe. And if you worried about having to inject yourself 3 times instead of once,...just imagine being diabetic and doing in 12 times a day.
Do you have a blood sugar meter?