Matt 10:22, When you are enduring, you are receiving a deliverance (salvation) by the act of enduring. You will not make all scriptures harmonize if you persist on using all salvation scriptures as eternal. Mat 7:21, Throughout the scriptures there are several names that are referring to the church that Jesus set up, the kingdom of heaven, the church of God, the church of Christ, the little flock, the remnant, the bride of Christ, the church of the first born, the church in the wilderness, the new Jerusalem, and more. The church is also referred to as, the few. In the same chapter in verse 13 and 14 The wide gate are all of God's children who are believing and teaching a false doctrine, and the strait gate are all of God's children are a part of the church that Jesus set up and are teaching his doctrine that leads to an abundant life that we can live here in this world. and few there be that find it. This "few" is not talking about the amount that will enter eternal life because they are numbered as the sand of the sea and the stars in heaven.
The standards are the same for all Christians, it does not matter who is being talked to.
Rather it is Jewish Christians, Gentile Christians, Hebrew Christians, Roman Christians, or any other name you want to place before Christian. The standards for all Christians is the same.
Second Matthew 10:22 is not talking about enduring to be saved through physical life in the flesh, else all the Apostles were failed as they all were killed but one who was exiled;
Peter- crucified upside down
Paul- beheaded
Matthew- slain by a halberd
John- exiled on Patmos
James- put to deat by the sword by Herod Agrippa ( Acts 12:2 )
Andrew- crucified by Roman Governor, Aegeas( Aegeates )
{ bound not nailed to cross to prolong suffering }
Bartholomew- beaten with rods and then beheaded
James, son of Alpheus- beaten, stoned, then clubbed to death
Thomas- thrust through with spears, tortured with red hot plates, and then burned alive.
Philip- tortured, stoned, crucified upside down
Simon- crucified and/or sawed in half
Judas Thaddeus- beaten to death in Mesopotamia
Judas- committed suicide for betraying Jesus
Matthias- (replaced Judas) stoned to death