Theists, is the Heaven inside the Universe?

No. The spiritual heavens are not part of the material universe and the material universe is a relatively recent creation. The spiritual heavens are beyond the reach of human tools or instruments.

The Kingdom of God is 'at hand' - so close you can touch it.

It exists in a different dimension.

Jesus is the real life time-space PORTAL into it.

"I am the way, the truth and the life. No one comes to the Father except through Me."

That exclusive statement by Jesus rules out establishments, traditions, regulations and all 'man-made' efforts to get to God, and therefore ultimately, heaven.

One God, only one way to Him.

The way is a person, not a religion.

Theists use to think heaven was the clouds. The people who wrote the Qur'an, bible ect. Couldn't comprehend space.

Heaven isn't in the sky, except when it is.

It all depends on which answer will contradict the argument of the person asking the question.

I'm amazed at the number of people who claim to be experts on the supernatural when , by definition it cannot possibly exist outside of the imagination.

No, of course not. "Supernatural" means "beyond the natural". The universe is part of the natural.

That is not a theist question , it is a (revealed) religion question.

It could fin on the head of a pin.