Magnification is simply a reference to the amount of enlargement from either
a) The size of the real object to the size of the object on film/sensor. This is constant regardless of the size of the format, so magnification never changes with format when you are talking about lens magnification. I.e. a 1:1 macro can always do 1:1 on any format. Now, 1:1 on a crop body is a smaller object than 1:1 on a larger sensor, but it's still 1:1...the projected image is life size.
b) Magnification from sensor to print. Obviously, you are enlarging a crop sensor image more than an uncropped full frame image when printing. (I.e....printing an APS-C image at 8x12 inches is magnifying the sensor 13 times...printing a full frame image at 8x12 is magnifying the sensor 8 times.) This is regardless of pixels, as pixels enter no part of the equation. What should tell you this for certain is that there's no standard format for pixel size or density.
Yes, but if all else is equal (lens, distance from subject), you will have a 'larger' image from the FF sensor. To get exactly the same 8x12 image size (i.e. pictures are the exact same, except for the things like IQ, DoF, etc.), you would have to shorten the distance from subject, use a longer lens (zoom in more), or crop the FF image, all by a factor of 1.6. If you hold focal length and distance from subject constant, and crop the FF image to give you the same image 'content', you will magnify that section of the FF sensor 13 times, to get that 8x12 print.
Simple test, put an EF-S lens on your 30D and shoot a picture. Now take an EF lens @ the same focal length and same distance from subject, and shoot the same picture. The image 'content' will be the same. Things like sharpness, IQ, etc. may be different, but other than that, they'll be the same image. Focal length is focal length. I did this w/ my 40D using my EF-S 17-85 @ 70mm and my EF 70-200 f/4L @ 70mm (both @ f/8) and other than the obvious differences due to lens quality, both images were the same.