How will less flour affect molten lava cakes?
If you're not getting the exact results you want, I suggest you experiment with a few things and expect a few learning experiences along the way. Look at three or four other recipes and look for ideas of things to try.

As noted in the comments you might want to adjust cooking time and/or temperature. If you're oven is too cool you might have cooked the inside more to get the same external look than if it had been at full temperature. So try more heat or less time. If you think it was too soft inside do the reverse.

That said, it sounds like you don't really like the intended results from the recipe, so you'll probably want to make other variations.

Depending on how things are combined in the preparation process you can try experiment with flour and fat levels. Remember that if you liked the outer layers adjusting the flour will effect those too. Some recipes include unmelted chocolate pieces put into the cake as you pour it into the dish. That will give you more of the texture you see in the first picture (the heavier chocolate will depress into the weak structures below it). You might also want to try adjusting the overall chocolate amount and how much butter you melt into it.