your reply is problematic. there is in fact only one Church there has only ever been one Church
Yes - i's ALL Christian believers.
All who confess Jesus, trust Jesus, serve Jesus and believe that he is the only way to the Father.
The church can be found where Christians gather - in coffee shops, Bible study groups, Bible college, school or university Christian unions.
It can be found at Greenbelt, Spring Harvest or New Wine (UK Christian festivals) where thousands of people from all denominations gather to worship God, read his word and pray together. It can be found in the quiet of an abbey, monastery or convent.
individual parishes, instantiations, as you put it, are not the whole church.
They are local congregations and part of the one, holy Catholic and Apostolic church.
and it is that church the one church that St Paul wrote about in First Timothy 3:15.
Paul founded several churches - local congregations - at Ephesus, Corinth, Philippi, Thessalonica and so on.
I do not think you're going to get any unity out of reducing discussion to the most general propositions you can think of.
It's about finding what we have in common and all agree on - also, those things that are the most important.
Differing church practices are not the Christian Gospel.
Even The Nicene Creed is a little bit specific for the kind of generality you seem to be wanting to move towards.
The Nicean Creed was written to counter the false teaching that was going around at the time and which centred on who Jesus was. Some said that he was only human and not divine, some said that he was only divine and not human.
The question that Jesus asked his disciples - "who do you say that I am?" - is still the most important one that anyone will have to answer
Salvation is by him alone.
If you really do want to limit the Creed to Confessing Christ as Lord and Faith in the risen Christ then you could not exclude Jehovah's witnesses Mormons or a number of others sects that Christians generally have rejected.
"Lord" is not a human title of respect. And if we believe that God raised Jesus from the dead, that necessarily means that all that Jesus claimed about himself - being one with God, able to forgive sins, entitled to use the name that God revealed to Moses, the one who came from heaven and has seen God, the only way to the Father etc, etc - is true, Romans 1:4. Why would God raise a blasphemous, deluded/sinful man from the dead? JWs etc do not believe that Jesus was God.
You would need to at least add The holy trinity and the incarnation and the hope of resurrection for Christians and The final judgement and The communion of Christians to your creed.
Accepting Jesus = accepting his teachings and all that he claimed about himself.
He said that he was one with the Father and that the Spirit is God's Spirit. He forgave sins, etc. The Jews believed he was claiming to be God, which is why they tried to stone him, John 8:58-59 and then had him crucified for blasphemy.
Jesus said that he had shared God's glory before the creation of the world, John 17:5, and had obviously been born as a human - God in the flesh; incarnation.
Jesus told his disciples that there were many mansions in his Father's house, that he was going to prepare one for them and that he would return and take them to be with him, John 14:3.
Jesus spoke of final judgement - eg Matthew 25; sheep and goats.
In order to be faithful to scripture there would be a whole lot more you would need to add to your creed, baptism, the Lord's supper, marriage, ordination, church governance,
Jesus taught baptism and the Lord's supper. He did not teach about ordination.
in which case I think that you might want to go back and formulate a clear statement of your own fundamental beliefs, to compare and contrast with those the Catholics hold, or that the orthodox hold, or Lutherans, or any other group with which you wished to conduct a discussion leading to unity.
All Christians accept Jesus, therefore, should accept who he was, what he did and the words he taught.
There are many different ways of putting his words into practice - e.g. what is baptism? What is worship? But what we have in common is that we accept, have received and trust in the One who said them.
What we should be doing is encouraging one another in the faith and into a deeper relationship with Jesus and not focusing on church practice.
The very words "church which Jesus founded" - which you believe to be synonymous with the Catholic church - are a sign of disunity. It suggests that any Christian who goes to "another church" is in one that is not founded/recognised by Jesus. The "we're right, you're not" attitude is how wars start.