Greetings all, and welcome to the forum Pamsel, sorry I've missed out on all the fun so far, Marie pm'd me (& Evan) to take a gander at this thread. Let me take a whack at helping this 'Pamsel in distress'
The info you've received thus far is good, I see a couple things that haven't been adressed. :
You did the partial drain and refill, which water source did you use for the refill? Your TA increased, instead of going down, I suspect you used the community water and that it is high in TA (& possibly iron) have you used the same source to 'top off' the pool for the past 5 years? I don't want to give you more work, but I do want to help you, please have the community water and the pond water tested for the usual perameters and metals and let us know the results. (I'm thinking that the pond water will test better than the community water, and will be your prefered (though not optimal) method of filling the pool, a little pond scum can be dealt with by a bottle of bleach, high alk and metal tap water will require more costly chems and more time to correct)
I can't remember if anyone told you about the problem of cya being algae food over the winter, Ben has a riff on it somewhere (could one of you computer literate folks please link it up - who knows what would be the result if I tried) and he says it can take a ton of bleach to get the problem taken care of.
One last thing, I'm hearing thunder and don't want to fry my pc, when using the sequestering agent, place a chlorinating tab in the skimmer, you need the cya anyway, it'll help the metal come out of solution in the filter where it belongs. As for adding granular cya (stabiliser) put it in an old kneehigh or pair of pantyhose and just drop the packet in the skimmer.
Thanks for the compliment Marie in asking for my input! I hope this adds a little to the thread and lets Pamsel get swimming soon!!