You are correct regarding the Co2 in the water. I have charts that estimate the waters corrosivity potential in relation to pH and c02, but I am out on a business trip for the next week. Maybe someone else here can provide some better insite. I dont do the c02 charts often enough to kow the exact formulas, but looking at your report, I am not surprised that you are seeing some copper staining and erosion. Many companies look only at the pH, this is usually adequate. This is a great example of why regional water dealers are usually preferred when it comes to well supplied water since the water treatment methods can be very difficult to properly and adequately treat.
C02 removal from water can be simple, or complex depending on many factors. I would recommend calling a local water guy and ask if they are familiar with your particular issue. You should know right away if there level of expertise is adequate by there reply.
Degassification of water can be done through aeration, membrane (liquicel) technologies, or through sacrificial medias like calcite and corosex. pH plays a large role in the systems ability to function properly. and with the high level of co2, you may raise the hardness considerably.
You could try a simple pilot test to see how calcite or corosex will work if you do not want to pay a professional. Simply install a filter housing with a calcite an/or corosex cartridge, run the water through it at approximately .2 GPM for an hour, and have the water retested for c02, pH, and hardness.
Your softener will have to be sized according to the new level of hardness after the calcite filter, if it works.