In the early days of pizza making in the U.S. where the pizza operators used very high temperature ovens (mostly coal-fired) and baked on a stone surface they could not use sugar in the dough for the very reason you discovered. That still applies today even for deck ovens, which overtook the coal fired ovens (and wood-fired ovens) in popularity.
As for the vital wheat gluten, one of the steps that is often recommended when using vital wheat gluten as part of a dough formulation is to add 1 1/2 to 2 times the weight of vital wheat gluten as additional water. In your case, if you did not do that, then the oil perhaps helped get the fluency of the dough you wanted.
What I do when I use vital wheat gluten is to replace part of the formula flour with an amount of vital wheat gluten that will produce a final blend with a desired protein level. I then adjust the hydration if needed. As an example, if you have a base flour with a protein content of say, 12.7%, which is typical of bread flour in the U.S., and want to increase that to 14.2%, which is typical of high-gluten flour in the U.S., you simply replace part of the base flour with an amount of vital wheat gluten that yields a total blend with a protein content of 14.2%. I do the calculations for this sort of exercise using member November's Mixed Mass Percentage Calculator at http://foodsim.unclesalmon.com/.
If you want to play around with that tool, you will want to know the protein content of your base flour, the weight of that base flour used in the dough formulation, the protein content of your vital wheat gluten (65-75% is typical), and the targeted final protein content. To convert the calculated weight of vital wheat gluten to a volume measurement, you will also need to know how much a particular volume of the vital wheat gluten weighs (e.g., 1/4 cup weighs 30 grams). All of this sounds quite complicated but it really is not. If you decide to use the tool and need help, let me know.
BTW, you have done a great job working with, and understanding, baker's percents. Do you do the calculations long hand or do you use a calculator of some sort?