first of all, shenron is not omniscient, the profile says his intelligence is average, second of all, the question how to find the super dragon ball in universe 6, and Shenron said that he can't, because he is not that mighty (aka, he is not that powerful)and the universe is very vast, he never even says that the universe does not have a center, just that it is BIG, man please.
again, two things can be true, you can say that the earth is big from our perspective, that does not mean the earth is a never ending thing.
SEE THE SCENE, Jaco tells Bulma that the universe is very big, he does not deny that the universe has a center or edge, he tells her that the universe is still big, big enough to hard to find something ON THE CENTER of the universe.
Except how the hell could the future version build a time machine if he had no knowledge? Again, future Bulma, built a time machine, with few resources, the Bulma from the present not being able to do it is just because of time.
how did bulma from the future build the time machine if she also didn't have notes?
could you show me the part where Jaco said that Bulma is wrong about the universe having a center?