I live in Central Florida, where we talk about 100/100, 100 deg. and 100% humidity. In any case, a couple of years ago I worked to recreate the french bread I had while visiting France for a few months. I used a recipe not dissimilar from yours. Don't ever use margarine however, it's really bad for you and the outcome isn't worth wasting the other ingredients. There are three things that eventually made the difference, two of which made the biggest difference.
The first, and biggest difference in the quality of my bread, was using a "Starter" or a "Sponge". This is 1/3 of the flour, all of the yeast, and enough water to make a pasty ball that is then dropped into a deep pot of warm water. When this rises to the top you then use it with the rest of the ingredients to complete the recipe. It makes an incredible difference. Did you know some "starters/sponges" in France are decades old?!?! You can manage one for years if you want but I start fresh each time; though I did leave one, after it rose, in a bowl on my counter for two days to try a version of San Francisco Sour Dough and it came out really good.
The second and close contender for affecting the quality was a good Stone. I don't care for the synthetic type, way too small and not enough mass to do the job, so a waste of time and money. Go to a Stone yard and pick out a flat, dense stone or sandstone that is larger than a rack in your oven and at least an inch thick, more than 2 is likely a waste. It should be heavy enough that you will probably need to have someone carry it for you, chip the edges down to fit into the oven (go slow, take small chips else you'll be back at the stone yard for a new stone) and then get it into the oven laid onto one of the racks. Make sure it covers at least 90% of a rack.
Before using it cure it by running the oven at 250 to 300 for at least an hour and then 350-375 for at least 40 minutes. Don't open the door and let it cool at least 15 to 20 minutes before you do open the door. You want to do this to not only cleanse the stone but to drive out as much moisture as you can that might crack the stone if you simply popped it in and cranked up the heat. A good stone turns most ovens into much better ovens, so just leave it in there, cookies, pies, pizzas, bread, everything just simply cooks much better. I've even had a "southwest" steak cooked directly on one, it was really great. Anyway, clean it with a scouring brush or wire brush, ***never*** with chemicals as the stone soaks these up and gasses them back out when heated. If you chemically clean your oven take the stone out and clean it separately.
Lastly, the technique of rolling the inside of the bread outward in a skin-forming, lightly stretching exercise while forming the loaves is actually important to the interior of the bread. I think it has to do with creating the right thickness of gluten-skin that will hold the moisture in the inside while escaping at just the right rate through the skin to cook the interior and the outside crust correctly. The topmost, outer crunch by the way has to do with the egg, milk, or butter surface brush you use before popping your loaves into the oven. Don't forget to lightly score the loaves before putting them into the oven, toss a thin layer of corn meal onto the stone for the loaves to rest on and when done baking let the bread rest at least 10 minutes before digging in and trying it.
Last note, I assume you have a kitchen that is served by Central Air Conditioning. So while humidity will absolutely affect the outcome of your bread making (you're not likely to create the same bread made in Avignon or Phoenix for that matter), not following or incorrectly applying certain techniques will greatly affect your bread quality. Two references I used were Madeliene Kammen's "When French Women Cook" a good read besides a good cookbook, and "The Way to Cook", a new version is available as "The New Way to Cook" and is an excellent cookbook in many ways. Also, I recently caught an episode of Alton Brown's "Good Eats" show that gave a decent review of forming the outside skin. Madeleine Kammen goes into greater detail but seeing it is definitely helpful. The skin forming practice was the only tedious part of the process for me as I only had a description at the time and I didn't understand it's importance or purpose at the time. Once you get it down however, it's not a chore and just a natural way of forming the look of the loaves you are familiar with.
Remember to just have fun and enjoy the less than perfect attempts with a glass of good wine and your best butter, jam and or cheese. It won't take but two or three attempts to get you great bread, keep at it and you'll have the best boulangerie in Northern Florida. Bon Chance.