I too am fascinated by things like this. There is every reason to believe the Universe is infinite. If you imagine a rugby ball, even the smallest measurement from A to B will show a slight curve, demonstrating there is a limit.

No matter how vast the a to b measurement, no curve is apparent.

There is speculation that the rules of the Universe may change the deeper you get into it.

For example, a fish in the sea will not be able to swim into an iceberg, or stand on it. The rules are different. Likewise any change in the rules in the Universe may mean we can only go so far. But there is a beyond.