I would try making a small batch before trying a 50lb bag of flour. Again, I like the results of a two day cold rise before using the dough. Remember that you will have to let some of the air out of the dough, as it will bubble up a bit, but that is OK. The flavor will be there.
As for the beer, I have found Belgium style beers, double bocks, Extra Special Bitter beers, Oktoberfest beers, and hefeweizen beers to work well. (Can you drink all that in, in one sentence?) I only stay away from beers that are the heavy Stout beers. They tend to mess up the dough and darken it too much. However, since a Porter is a step under the stout, it should work. You can see that I too, have used some darker beers on this thread. Keep in mind that I use Power flour by Pendleton Mills. I am not sure how a dark Porter would work in a Caputo 00 flour? Again, it is a fun experiment and I would love to see your results.
As for my thread, you can see that i try all kinds of beers, but it is hard to beat great beers like Samuel Adams, Blue Moon, Red Hook, and etc.. Both in flavor and price. And don't forget beer that is brewed locally too. I have found some great beers brewed in my neighborhood as well.
Over all, experiment and enjoy yourself. Sounds like you on the right track.