Sorry for the delay, out mowing the lawn.
You seem to harbor some misunderstandings about astronomy. I have assumed a constant speed of light, because it works. If you change the speed of light, physics changes. The most fundamental equations in physics are based on the speed of light, and if that changes, strange effects would be observable, such as the visible spectra of stars and galaxies would be unrecognizably different (unlike the recognizably different effects you get from redshifts), as well as other effects. Remember, a certain type of star in another galaxy looks exactly the same in every observable catagory measurable is the same type of star in our galaxy. This means that the physical laws that exist in that part of space is the same as the physical laws in our part of space.
I'm not saying speed=distance. What I'm saying, since the speed of light is constant, is that for every light year a photon travels, we are looking back one year in time. That means if a star is 3.16 light years distant, we are seeing photons 3.16 years from when they were emitted.
Remeber, that laboratory experiments concerning the speed of light take place in a special medium, which is not the same medium as that which exists in space. If that medium were to exist in space, it would have to exist in a finite sphere, only around our sun and no other (I'll leave that thought experiment to the reader), and not exist around any other star. Why would you think that physical phoenomenon would take place like that?
There is also some evidence that the speed of light is in fact slowing and it has been measured to have slowed down over time.
I'm assuming you are referring to Setterfield's work on C-decay. It doesn't work, for the reasons I explain above. It's impressive, though, the contortions he tries to go through to get it TO work, however unphysical they might be.