Your texture certainly looks good. In part that's probably a product of the protracted first rise, so we don't want to change that too much. Whether it's making that big hole on top is somewhat in doubt. All I can tell you is that letting the first rise go too long often has that effect. I wish I could give you a certain answer but I can't.
Good baking technique requires you to let go of the clock in favor of the dough's appearance. I don't mean to sound snarky or superior because I recognize the convenience, the comfort, and the assurance of using the clock as the primary metric, but double means double and not sixty minutes. Every time you make a yeast dough, you're making a new culture. And every culture is different and will respond somewhat differently to the ambient conditions -- which also vary.
The more you bake the more you learn to rely on your eyes, nose and fingers and the less on your clock and measuring spoons. Think of the clock's function as telling you when to start paying attention. Think of your measuring cups and spoons as less accurate than your fingers and eyes. And think of someone else's recipe or technique (including mine) as an intermediate step to developing your own.
As a way of facilitating that paradigm shift -- Bread is always four things and always within a rather restricted range of proportions. A bit more than six cups of flour, requires about 2-1/2 cups of water and a tbs of salt, and an amount of yeast roughly equal to 2 tbs of "instant" yeast. You can use different yeast cultures which will require a different amount. But other than that, that's bread. Every other addition is a minor variation. Break almost any bread recipe down into liquids, flours, etc., and you'll find those four things in similar proportions -- whatever else is in there.
When I wrote about the proportions, I was never very exact. Everything was "roughly," or "about" or "a bit more." That's because there is no exact proportion for making bread right. Not ever. It's a look, a feel, a smell. We keep our yeast and flour proportions fairly constant (for any given type of yeast) because that comes so early in the process and because variations in timing can compensate for variations in the ingredients or ambient conditions. Liquid we add to suit. In that way, every bread is couture.
Here's some technique: If you're using a stand mixer to knead, measure in 2/3 of the recommended liquid as the last ingredient, start the mixer, let it mix the dough, then start adding liquid until every bit of flour is picked up from the bottom of the bowl. If the dough doesn't clear the bowl, i.e., if it still sticks to the bowl, sprinkle on just enough extra flour so the dough comes away cleanly.
Knead about 20% less than the recommended time (time to pay attention, remember), take the dough out and finish kneading by hand. The first thing you should notice is whether the dough is sticky or not. Most bread doughs should be sticky. They should be just dry enough so the dough prefers to stick to itself, rather than your hand. But ... a bit wet and a bit sticky is what you want. And the only way to know is to feel it. To feel every part of it. In other words, to finish kneading by hand.
When it's kneaded, oil it lightly to keep it from drying out and keep the surface flexible; put it somewhere it can't escape (your tub is fine); and let it rise. How long should it rise? To about 2-1/2 times its original height, which is the proverbial "double in volume" (didn't know that, did you?). There's no particular number of minutes. That depends on how active the yeast, how sweet the bread, the temperature, the humidity, and a number of other factors. Is the timing important. It's important but not critical. Your hole on top is one reason it's important.
Why am I telling you all this when all you want to do is fix the hole? To make bread making the artisanal and satisfying experience it should be for you instead of a task. To give you mastery.
A great pleasure,