Don't knock Aikido and Tai-chi, both are very effective when mastered. I also keep plenty of toilet paper for an emergency and bullets because those things never go bad. Reading an account of a fellow who lived through a societal collapse he suggested that what you really want are a lot of DVDs because you will be spending a lot of nights at home. You will be able to go to a movie and the theater will have private security but you will have to get there and back and that is where you are vulnerable. He also suggested having a truck with a brush guard in case you have to drive through a crowd or mob.
And you forgot water, I keep several gallons on hand because it can go out or turn brown and be undrinkable at any time.
I'm not a tai-chi expert but I spent 4 years doing Aikido - it was an interesting art and taught me some useful knowledge, but as a self defence art on its own it would potentially do more harm than good giving practitioners a sense of false confidence. There are far more effective arts that can provide simple and effective techniques at an early stage and then build on them. Perhaps the most effective art is british or thai boxing - simply because it teaches speed, evasion and fitness. It's amazing how tired and disorientated you get when you're in a proper scrap. None of the Aikidoists I've ever trained with would last 2 minutes if it came to the crunch, even the high degree black belts. I did however enjoy it, hence 4 years of doing it. It's a beautiful meditational art when you master a technique.
Yes, you're right on water. It's the most important thing. If we don't drink we're in trouble within a week. I guess because I'm in the UK there is no shortage of rain.
There are a number of options to purify and clean dirty water. Bits of charcoal, coffee filters, tea towels and kitchen towel can help to filter it, a drop or two of bleach can kill bacteria. The plastic bottle in the sun technique would work better in a warmer climate.
I have a couple of 20L barrels of water that I just refresh every couple of years which would get me through a week or two if I only used it for drinking. It might be a bit stale but it would get me to the point where I could source more.