As far as the CYA goes, I believe you have two options.

1. Do a partial drain and refill to reduce the CYA level. This is the only method to remove CYA from water. I'm sure it's not a very desirable option given your location.

2. You can successfully manage a pool with a high CYA. You still need to know what the CYA actually is, and you still use the best guess chart and every other part of the BBB method.

If you want to use option 2, you need to get some distilled water from your local grocery. Dilute some pool water 50/50 with the distilled. Perform the CYA test on that water, multiply the result by two. Hopefully your CYA won't be over 200, if so - further dilute, retest, and multiply appropriately. Personally I'd give up on option 2 with a CYA over 200 and bite the bullet on a little refilling.

As far as chemicals to keep around, that depends on how often you make it to the grocery store. I generally try to keep a month or less worth of most chems. Liquid chlorine/bleach doesn't keep all that well so I would not buy a huge amount unless you're planning to use a lot.

Both dichlor and trichlor add CYA to your water. If you weren't already aware, that's probably where you got into trouble with the CYA. You should immediately discontinue their use until such time as you want to increase your CYA level again. Nothing but bleach, or "Liquid Chlorine" for your sanitation. Those are the same thing, except liquid chlorine is usually sold at a higher concentration.