You can cut that old bond lug off the wire. Each piece of equipment in your system, except the heater, should already have a lug attached. The heater bond lug comes in the parts bag (along with an attaching screw) and has to be attached to the cabinet by the installer at the lower left or right side of the heater (right in your case). There will be a small hole in the cabinet to accept the screw. If you don't have the screw and bond lug, they can be purchased at most hardware stores for very little. I believe the screw size is #10 sheet metal. Get stainless steel if you can. Just force the screw in as it will make its own threads.
The bond lug on your pump is below the plastic cover on the back of the motor. Turn the power off, remove the cover (1/4" nut driver) for easier access. Small flat-blade screwdriver for the lug.
Get enough #8 bare copper to reach your heater and the ProTek. You can use a "split nut" to attach the new wire to the old. They look like the picture and can be obtained at most hardware stores. Be sure to tighten the nut very tight.