I think there are many problems with the way you design your thought experiment, and the conclusions you draw form it.But it's ok, we can try to go through some of what I think is the most problematic points.
I will try to do so without any form of math because I might be wrong, but I don't think you are very comfortable with formal science (my apologies if I got it wrong)
1) The way you make assumptions. First you assume that a giant several light-years tall could exist. I'm not saying that it is a problem that there is no such thing. The problem is that it is likely that no such thing could physically exist. Scale effects might imply that such a huge living organism doesn't obey the laws of physics. If the system you are thinking about is not physical, then your conclusions will most likely not be either. So you should be aware of that first big assumption out of the blue. You should provide some arguments on the validity of imagining such a monstruous thing. Quite often, the devil is in the details (think about the famous example of a light-year long stick that you wiggle around. The transmission of information to the far end of the stick could apparently occur at arbitriraly high speeds. The solution lies in taking into account the compressibility of the stick, which implies that the "mechanical signal" itself along the shaft has a limited speed. Your example is actually similar, and same argument might be one way among other to correct your thinking. Pay attention to details, make sure what you imagine respects the laws of physics)
Second, you assume that the step would only take a bunch of seconds from the giant "point of view". Why ??? Not to mention that I think you have some confusion on the notion of "point of view", it seems quite obvious that the step of an elephant is much slower than the step of a mouse. Why would you assume that the step-time is size-independant ? this is a HUGE assumption, which seems completely wrong to me. Your giant might cover a long distance, but it will probably take him a very long time. Think about the "ents" in Lord of the Ring. Accelerating the huge mass of his legs with such great magnitude would require insane amounts of energy. It's heavier, so it's most likely gonna be much slower. Of all the supraluminal travel device I've heard about, this is probably the most far-fetched and one :)
2) Your comprehension of the subject you are tackling : I might be wrong, and I'm sorry if I am, but it seems clear to me that your understanding of physics in general, and relativity in particular is limited. It's ok. So is mine. But before trying to break some theory that has been around for a century, and extensively challenged by the greatest minds of mankind, you should at least do a thorough research on the subject :) I'm not sure you understand the actual arguments between the impossibility of speed-of-light travel for a massive particle (if not you should at least check out lorentz transformations, infinite energy problem, etc...) That is the first step you should take. Don't wonder "how can I make it possible" before you wonder "why do they all say it ain't ?"
3)The way you draw your conclusions. First, I would like to remind you that, strictly speaking, in physics, a thought experiment is never considered a proof of anything. Experiment always has the last word. Of course, for a chill discussion like this, it is still interesting, but never take the conclusions out of a thought experiment too seriously.
That being said, I didn't look too much at your conclusions because the thought experiment is not valid for me. But they make me think again that you are not comfortable with the basic notions of relativity("light would speed up from the giants point-of-view" = "Fuck you, Einstein"). Finally, a big problem is that you lack the potential conclusion : "my thought experiment is ill-designed, and nothing should be concluded from it". This is always an option to consider, even for the greatest geniuses :)
I hope you won't take my comment in a bad way, but I think it is important to talk about the potential flaws on the basics, which should prevent us from going any further