1) In this essay, I would say the two views of time that are involved are the idea of infinite time, where the years "don't pass", and the circles that time takes us on, as he moves from boy to man, son to father.
2) At the end of the essay, White is struggling with two different things.
First, earlier on, he is struggling with the  passage of time and how increased technology changes the lake for him. For example, the motor boats now have louder engines and this disturbs his view that the lake is constant and never changing.
The second concept he is struggling with is how time is effecting him. White says at the end of this story, "As he buckled the swollen belt, suddenly my groin felt the chill of death." I would say that this means that White finally feels as though time as has caught up with him, and he now feels death closer then it ever had been before.