How can I put a Lens Flare in the exact same position consistently across let's say 6 different images? Any ideas?
Yes, I have many, including one that should be of service to you.
Select the Eyedropper tool.
Choose Window > Info to open the Info palette.
Position the Eyedropper over the center of the proposed flare.
Use the Caps lock to change the tool to the more precise crosshair, if necessary.
Note the X and Y coordinates in the Info palette. Write them down.
Choose Filter > Render > Lens Flare
The Lens Flare dialog box opens.
Alt (PC) Option (Mac) + click on the Preview window.
The Precise Flare Center dialog box appears.
Enter the X and Y coordinates you jotted down earlier. You did write them down, didn't you?
The flare is placed in the exact position.
Repeat as needed.
Even better, create an Action to do it for you.