Gentlemen,
I think we all know and see that something is coming. Obviously the most important thing is securing a network of likeminded friends to rely upon, stacking gold/silver/lead, and having water/food supplies on hand. What goes hand in hand with this preparatory planning is physical training. I would recommend functional style training, along with a STRONG foundation of cardio. Don’t fall for the body builder meme, start running NOW. Over the last two months I have gotten my mile time down to 8m/mi for a sustained 5 miles. Building your body’s “gas tank” so you can push harder, go further is integral not only to building mental hardiness but also may be the difference between life and death.
Start running. Today.
RE antibiotics -- mostly solved with soap, and soap can be made from animal fats and lye, which can be made from ash. I can't think of the last time I used antibiotics at all, and I am much healthier for it.
RE gunpowder -- that's really high up in the "tech tree" so I stockpile ammo. I believe actual gunpowder is easier to make consistently than blackpowder. At one point I was considering starting an ammo factory just so that my community would be able to make their own. The truth is I don't need many bullets to keep my property secure.