My advice, for what it is worth, I never use a Stout Beer. I only use beers that are not any darker than an Amber color. Also, when I add beer to my pizza dough, it is only 60 percent beer and 40 percent water.
I am curious what flour you used? Is it a high gluten flour? (High gluten is a must, at least for me.)
How much time did you give it to rise? (I do a cold rise in the refrigerator for a minimum of 24 hours, ideal time is 2 days in the fridge.)
How much total liquid do you add per flour? (I use 12 oz total liquid, one Tablespoon of Olive Oil, for 4 cups of flour, sometime one oz more of water, depending on how dry the flour is looking)
Take a look at my thread...."Using Beer instead of Water in the Flour?
" on this same section (Ask the dough Doctor). It will give you a step by step instruction.
In conclusion, I pressed out two pizzas doughs tonight. Here is one press out and another one to go. I put a Roma Tomatoe in the photo to compare the size. This was a 14" pizza. The beer I used was, "Samuel Adams, Double Bock".
DON'T GIVE UP!!!!!!! it took me a while to get it right too. You can do this!!!!!!!!!!!!!!!!!!!!