Harry,
I think you are listening to the pool store too much. Your pH and your copper are two separate and distinct issues. Don't combine them in your mind. They don't effect each other.
Now, the pH
What we are talking about here is basic chemistry. If you add the correct product, the pH WILL go up. Several years ago I helped a friend with his pool. All he ever used were pucks to chlorinate his pool and his pool and his also showed a pH of 6.4 Pucks are acidic and push the pH down. Overuse without adjusting the pH and your pH will go waaaaaay low.
Why 6.4? Because with many test kits this is the lowest pH the test will register. So, you may be WAY below 6.4 and while your additions are raising the pH, it just isn't getting high enough to register on the test.
So, with that being said -
You need to test the Total Alkalinity (TA). As long as it is above 50 things are good. If it's below 50 we will need to address teh TA first.
What you need is Borax. Borax is available as 20 Mule Team® Borax Natural Laundry Booster. It is sold in the laundry detergent section of most larger grocery stores and some big box stores. Borax is best added by pre-dissolving it in a bucket of water and then pouring that slowly in front of a return. Now, how much. Well, in your 5,000 gallon pool 64oz (by weight) 61oz (by volume) of Borax will raise your pH from 6.4 to 7.2
Add that much to the pool and test the pH again after it circulates for 30 minutes or so. if it's 7.2 or above, you are good. If not, you will add Borax again. You will keep repeating this until you get the pH up on the scale where you can read it.
The Copper is a different issue and not as important right now as the pH. Lets get the pH in line before you worry about the copper.