I agree with the OP's theology. Indeed, Jesus stated this explicitly:
Luke 17:20, 21 - When asked by the Pharisees when the kingdom of God
would come, Jesus replied, “The kingdom of God will not come with
observable signs. Nor will people say, ‘Look, here it is,’ or ‘There
it is.’ For you see, the kingdom of God is in your midst.”
Thus, the kingdom of God, or the kingdom of heaven (interchangeable in this context) is defined by the spiritual followers of Jesus and technically compose that who are "Christians" (Acts 11:26), literally, "ones like Christ".
Paul says the same thing again:
Gal 3:26-29 - You are all sons of God through faith in Christ Jesus.
For all of you who were baptized into Christ have clothed yourselves
with Christ. There is neither Jew nor Greek, slave nor free, male
nor female, for you are all one in Christ Jesus. And if you belong
to Christ, then you are Abraham’s seed and heirs according to the
promise.
Indeed, almost every time the phrase "kingdom of God" is used in the NT it is to emphasize its spiritual nature and not its physical (or political) nature. Here is a sample:
- Matt 12:28 - But if I cast out demons by the Spirit of God, then the kingdom of God has come upon you. (see also Luke 11:20)
- John 3:5 - Jesus answered, “Truly, truly, I tell you, no one can enter the kingdom of God unless he is born of water and the Spirit.
- Acts 8:12 - But when they believed Philip, proclaiming the gospel concerning the kingdom of God and the name of Jesus Christ, they were baptized, both men and women.
- Mark 4:11 - He replied, “The mystery of the kingdom of God has been given to you, but to those on the outside everything is expressed in parables (see also Luke 8:10)
- Matt 21:31 - Which of the two did the will of his father?” “The first,” they answered. Jesus said to them, “Truly I tell you, the tax collectors and prostitutes are entering the kingdom of God before you.
Thus, Jesus taught that the kingdom of God is a present reality. However, Jesus also taught that there would be an eschatological fulfilment of the kingdom of God when He said:
Mark 14:25 - Truly I say to you that never will I drink of the fruit
of the vine again, until that day when I drink it anew in the kingdom
of God."
- Culture vs Bible Teaching
It is well-known that the Jews, and especially the Pharisees, were both racist and spiritually (and ethologically) proud and elitist. One of the functions of Jesus' teaching was to dismantle that elitism in His teaching in Luke 17:20, 21 and Mark 13:38. (See appendix below). Jesus summed this up when He said (quoting Isa 56:7):
Mark 11:17 - Then Jesus began to teach them, and He declared, “Is it
not written: ‘My house will be called a house of prayer for all the
nations’? But you have made it ‘a den of robbers.’ ”
Thus, the temple should have been open to all, including gentiles.
Therefore, the "dividing wall" was a cultural one and not a real theological barrier that had been false erected by the elitism of the Jews. Both Jesus and Paul emphasized this.
APPENDIX - Jews vs Gentiles
The covenant promises were always open to all people and was never exclusive. For example:
- Abraham’s own household must have consisted of perhaps 2000 people just to be able to raise an army of 318 men to liberate Lot, Gen 14:14. Indeed, Abraham’s chief servant (from Damascus) was clearly a believer and very devout as shown in Gen 24.
- The unfortunate story in Gen 38 about Judah and Tamar shows that a foreigner became the mother of the tribe of Judah.
- When Jacob entered Egypt, his family numbered 75 people (Acts 7:14, Ex 1:5). Some of these were not direct descendants of Abraham such as the wives of the 12 patriarchs, notably Joseph’s own wife. 215 years and four generations later at the exodus, Israel’s army had over 600,000 men, excluding women and children, (Ex 12:37, Num 1:46, etc) suggesting a total population of several million people, requiring many additions. This included a significant mixed multitude (Ex 12:38) showing that Israel obviously consisted of many non-biological Jews had joined. (Note that it is biologically impossible for Israelite numbers to have grown from 75 to several million biologically without many outside additions.)
- Moses married a Midianite (Ex 2:16-21) also known as a Cushite. Miriam and Aaron were severely reprimanded and punished for displaying racism (Num 12:1, 2)
- Caleb, who represented and led the tribe of Judah was a Kennizite (Num 32:12).
- Rahab was a Canaanite (Josh 2:1, 2, Matt 1:5)
- Ruth was Moabite (Ruth 1:4 16, 17, Matt 1:5) – these last two make King David descended from foreigners (Ruth 4:13-16).
- Uriah was a Hittite (2 Sam 11:3)
- King David’s elite personal (and very loyal) regiment consisted of Gittites, that is, Philistines (2 Sam 15:18-22, 1 Chron 18:17)
- Isa 56:6, 7 - And the foreigners who join themselves to the LORD to minister to Him, to love the name of the LORD, and to be His servants— all who keep the Sabbath without profaning it and who hold fast to My covenant—I will bring them to My holy mountain and make them joyful in My house of prayer. Their burnt offerings and sacrifices will be accepted on My altar, for My house will be called a house of prayer for all the nations.” See also V3.
- The Rechabites were Kenites (Jer 35:1-19)
- Many other foreigners lived in Israel (1 Chron 22:2, 17, 2 Chron 30:25)
- In Esther’s time “many of the people of the land became Jews” (Esther 8:17, 9:27)
- Even in NT times, many Jewish synagogues were attended by godly gentiles converted to Judaism (Acts 13:16, 26, 16:14, 17:17)
- Many Jewish proselytes came to worship in Jerusalem (John 20:20, Acts 2:9-11)
- Jesus quotes Isa 56:7, “My house shall be a house of prayer for all nations”, Mark 11:17.
