Guncollector,
First off , I applaude your forethought and I think that you've got a great idea. However, I have a few suggestions and minor criticisms. (BTW- I am a custom holstermaker by trade and as such have had a fair amount of tactical training. I will share some of that with you.)
Get some sound tactical training from a world class shooting school/instructor - NOT your local gunshop commando "expert". Look up Gunsite Ranch, John Farnam's DTI, Thunder Ranch, David Blinder, Chuck Taylor, Gabe Suarez or Louis Awerbach - any of these people will be able to teach you skills that you will desperately need to survive an armed attack. I grew up shooting starting at age 4, believe it or not. However, ten minutes into my first tactical handgun class made me realize that I knew absolutely nothing about self defense.
Get a concealed weapon permit. A weapon will do you no good if you cannot have it with you, and risking a felony charge is simply insane.
Add a decent defensive handgun, minumum of 4 magazines and 100 rounds of hollowpoint ammunition to your gear. My suggestion would be to go with a 9mm, unless you are a very experienced shooter. Under conditions of stress, hunger, fatigue (and possible injury) you will shoot it alot better than a larger caliber. A solid hit with a 9mm Cor-Bon or Hydra-Shok beats hell out of a miss with a .45. (You will be able to carry a lot more 9mm ammo for the same weight too). Get a good concealment holster, belt and mag pouch and (after getting instruction) practice with it until you don't want to even look at it - then practice with it some more.
Lose the alice pack - it screams "survivalist" and you will either be targeted by law enforcement or by terrified masses of sheeple, or
both. Get a nice yuppie looking daypack. Blend in.
Add leather work gloves and safety glasses to your gear, along with a
lightweight prybar. These will be worth their weight in gold if you have to dig yourself or someone else out from under post earthquake rubble, or jimmy a wedged door open to escape a building.
Add more water to your gear - in an urban environment with no electricity, it will be very difficult to find. During Hurricane Andrew in S. Fl, water hit something like $25 a gallon - when it could be found. (Which for a while was almost never).
Lost the big, monster flashlight. Someone suggested earlier a SureFire as a relacement - I could not agree more. A super bright, reliable tactical light is a great defensive tool, (in addition to being priceless when it comes to finding one's way out of a dark building, tunnel, parking garage, crashed aircraft, etc.) A small Photon II around the neck is also a great idea - get the red LED-it won't do too much to harm your night vision, and will be much less likely to attract unwanted attention.
I also agree wholeheartedly that you should get some training and add rappel gear (separate bag, in your office). You won't need to carry it around. You'll either use it to escape at the onset of "events", or it will sit there and gather dust. However, if you do need it, nothing else will do. Do not use military "greenline" or it's civilian counterpart "goldline". These ropes have outdates, and they are usually sold surplus after these have been exceeded. Get a 9mm-11mm Kernmantle static line.
Choose fleece (ie: Polartec) for warmth, with a breathable shell garment.
The Becker Companion is a good choice for your purposes. However, factory knives are heat treated in large batches and as a result, they sometimes vary in strength. Ethan (Becker) will replace any broken/damaged blade. Get one in advance, and abuse the hell out of it. If it does not break, resharpen it and toss it in your bag. If it does, then get a new one and try again.
Also, get a really good folding knife and carry it with you religiously. I would recommend a Spyderco if you want a great knife on a budget. A Benchmade AFCK in M2 steel would be even better. A Chris Reeve Sebenza would be tops.
Choose foods that do not require preparation - the light of a fire will attract unwanted (and perhaps deadly) attention from others (in the case of an earthquake, you might also set off explosions due to ruptured gas lines). Try your very best to go un-noticed as you make your way home.
Speaking of home, make sure that your wife is also properly trained and armed. It would be tragic indeed to finally make your way back only to find her having been harmed or killed by societies "jackals" in your absence.
I guess this is long enough. I hope that it helped a bit. After seeing the film footage of the WTC on 911, I wish that every American woud do what you are doing. God bless!