Hi Bob,
Maybe Heaven and The Kingdom of God are totally two different existences/places?
Not... really.
Many brethren are confused about this matter because they have failed to understand about the two separate dimensions of existence written of in God's Word.
1 Cor 15:48-52
48 As is the earthy, such are they also that are earthy: and as is the heavenly, such are they also that are heavenly.
49 And as we have borne the image of the earthy, we shall also bear the image of the heavenly.
50 Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
51 Behold, I shew you a mystery; We shall not all sleep, but we shall all be changed,
52 In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
KJV
What's the "image of the earthy"? Our flesh body.
What's the "image of the heavenly" Paul taught? The "spiritual body", which is not made of flesh matter, but of Spirit.
Like Jesus said in John 3, that which is born flesh and of the flesh, and that which is born of Spirit is spirit.
Yet per Revelation, and also shown about Eden in Genesis, God once dwelt upon this earth, His abode of His Garden of Eden was here, which is where the Tree of Life was, and still is, with Him, in the Heavenly dimension, a separate dimension behind a veil which we cannot see (unless God allows it, like 2 Corinthians 12 and Isaiah 6).
How is that possible, for God (The Father) to live upon this earth with us, as He promised per Revelation 21? John said God is a Spirit, meaning He has no flesh body.
So when Jesus was pointing to the Kingdom of Heaven being in our 'midst', He was pointing to our 'spirit' inside our flesh which God gave us, and it returns back to Him, with our soul, at flesh death. BUT... when Jesus comes to start His reign, and eventually, The Father is going to return to live with us, literally, and that will be on this earth, with BOTH dimensions joined. How's that?
We are given examples in God's Word of angels (who have no flesh body) eating man's food, and walking upon this earth, while in their "image of the heavenly" bodies. Some like to add to God's Word as if they somehow put on flesh bodies to appear on earth, but that idea is nowhere written in God's Word. Even Lord Jesus appeared on earth to Abraham in His Spirit body before... He was born in the flesh through Mary's womb (see Genesis 18; end of John 8).
So HOW is the Kingdom manifest today, since Jesus died on the cross and was resurrected? Simple, it is INSIDE US, in our spirit with soul; not our flesh for our flesh is of this present world time and destined to perish forever. The "spiritual body" Paul taught is the type body of the world to come. It's old Jewish doctrines that try to hang on to the flesh body for the world to come when that goes directly against what Apostle Paul taught in 1 Corinthians 15 and 2 Corinthians 5.