I'll weigh in on this one because I think I know what is going on (I'm in charge of Engineering).
First of all, on any scope, adjusting the diopter will change the magnification. That is just the nature of the beast. So, you will want to adjust it for the most true 1x for your eye.
Regarding the double image, I'm guessing that it has to do with where your windage and elevation adjustments are. This is also a fact of life on any 1x riflescope, if your W/E are adjusted way off of center you will see a double image with both eyes open, because the erector is tilted enough that the image through the scope is entering your eye at a different angle than the image of the target through your non-dominant eye.
Try playing with the W/E adjustments and see if you can eliminate the double image. If that works then it would seem that the scope is not pointing very true with the bore of the rifle. That could be any number of things, from the rail not being square, or something with the barrel, or the sight mount itself not being square with the optic. It's hard to say for sure without actually seeing the setup in person.
In any case, let's just take one step at a time. If you can confirm adjusting the W/E eliminates the double image then at least we know where to go from there.
Hope this helps!