“Unless you believe that one would eventually run into some kind of ‘wall’, the Universe is endless.”
That isn’t true; the universe is constantly expanding but isn’t endless. Time/space does not exist outside of it and in fact has no meaning outside of it. It is not empty space; there isn’t space.
In fact, the phrase “outside of it” is meaningless. And there is not an infinite number of stars.
If it’s constantly expanding, it’s in the process of effectively becoming endless. Where/when is the ‘end’?