OK.

You have three issues:

#1 - Your pH is WAY too low, and is corroding your heater. There's no way to tell right now how bad the damage is.
#2 - Your copper levels are WAY too high, and are likely to stain your pool.
#3 - Your chlorine is probably too low, but raising it will increase the chance of stains.

This makes it difficult. If you don't fix the pH quickly, you may loose the heater, and indeed, it may already be too late. But, in fixing it quickly, you run the risk of staining your pool, possibly severely and permanently. And, yet again, as the copper is removed, if you don't add chlorine quickly enough (but not too quickly), you run the risk of the pool becoming algae infested!

There is not simply and easy fix, and no matter what you do, things may not all turn out well. I'll try to help you plot a course as likely to succeed as possible.

So, do this:

#1 - Buy 6 boxes of borax and a cheap OTO / phenol red testkit (Walmart, or where ever.)
#2 - Turn your pump on, and leave it on 24/7.
#3 - Remove all chlorine from your pool -- tabs, feeder cartridges, every thing.
#4 - Stop swimming in the pool, till things are under better control. Swimming adds algae food.
#5 - Add 1/2 box of borax, slowly through your skimmer, every 4 hours. Test your pH before each addition. If the phenol red shows any sign of changing from yellow (which it presumably is, given your reported pH) and moving toward orange, stop your borax additions for 12 hours.
#6 - Find and purchase some polyquat algaecide (see www.poolsolutions.com/gd/polyquat.html ). But do not get the HTH brand; they are playing label games and it will be hard to get the right stuff. You'll probably need to go to a pool store. Once you've compared chemical names with the PoolSolutions page, begin dosing the pool per label instructions.
#7 - If you can find it, purchase a bottle of Jacks Magic Pink Stuff or Proteam Metal Magic. These are made of HEDP, a stronger metal sequestrant than the EDTA in Metal Free. But, do not use it yet.
#8 - Do not clean your filter excessively, but do clean it when it needs it. Hopefully, the backwash will be bluish green, indicating some of the copper is coming out on the filter.
#9 - Once you've added the polyquat, resume raising the pH until you reach a level of 7.4 - 7.6. At that point, your heater will no longer be 'under atttack'.
#10 - When you go to the pool store, get a complete water test -- chlorine, pH, alkalinity, calcium hardness and stabilizer -- and report those results here as soon as possible.

That's enough for the next few days. The copper will prevent algae till it's removed; the polyquat will help filter any debris, and prevent algae as the copper dissipates. I'm not sure how effective the EDTA will be at holding on to the copper. So, I can't predict how long this will take.

If you encounter any unexpected result, or especially water discoloration when adding borax, please report that here along with the test results. Don't worry about a copper test; it's not necessarily going to be accurate after adding all the EDTA.

Good luck!