Just wondering what is the reason that speed of light is the maximum speed in the universe?
I like the term which was used in the second volume of Landau and Lifshitz books. They started the argument by saying, that there is some finite interaction constant, which defines, how quickly the information is travelling. Which basically means, that there is no such thing as a rigid body starting instantaneously rotating as different sections of it find out that the body starts rotating at different times. Probably it's not an answer to this part of the question, but it's a different way to think.
Why there is no speed swifter than light? Or is it just we haven't found yet?
If you regard the speed of light as the interaction constant, according to which all the matter is interacting, then these questions should not be there at all, as they contradict to the assumption of interaction constant. However, this once again doesn't answer the question, but instead, pushes these fundamental questions further.
A similar question is like this: why the light speed in vacuum has to be 299,792,458 m/s? Why couldn't it be faster? Who is or what is controlling of this speed in vacuum? Look, in vacuum, who is stopping it from being faster?
I think, that teh speed of light magnitude is irrelevant, as it is just a numerical value which by luck happens to be this. And the value is this because of our chosen units. In other unit systems it is different (or it can be set to be equal to one).
Another question confusing me is this, if from a far far away Galaxy, its light travel to us and we see the stars tonight, couldn't it be fully possible that at this time, they actually are already dead?
Yes, as there is no way we can know what is exactly happening there at some particular moment.
So our knowledge is going to be forever limited unless we have something that can travel much faster than light?
Defintely, but this would mean the invention of a time machine, which would would break the causality phenomenon, which wouldn't be good. In a way, we will never explore the whole universe, as we are always limited by the age of the universe (or rather the distance light can travel during the age of the universe), and beyond there is the unknown.
Hope my rambling was at least a bit helpful.