1) Yup, think we can draw the line there.
2) Photons have zero mass, so I don't see how magnetism or gravity would affect them. Flexible speed of light would kind of crash most of the 20th century physics, really. But the beauty here is that when something "impossible" happens, science usually realizes it simply had the wrong idea of what's "impossible". So, I don't know, maybe the speed of light can be manipulated, but so far, as far as I know, the only thing that affects is what medium it's traveling through.
2) Photons have zero mass, so I don't see how magnetism or gravity would affect them. Flexible speed of light would kind of crash most of the 20th century physics, really. But the beauty here is that when something "impossible" happens, science usually realizes it simply had the wrong idea of what's "impossible". So, I don't know, maybe the speed of light can be manipulated, but so far, as far as I know, the only thing that affects is what medium it's traveling through.