My read of Lev 16 was about ALL the people of Israel, and I seriously doubt that all of them were believers in the Messiah. v.15 says "for the people", not "for the elect" or "for the saved", etc. I take that as everyone.
v.21 refers to "all the wickedness of the Israelites". Again, everyone.
v.29 includes the foreign born aliens (Gentiles) in the atonement.
v.33 says "all the people". Again, everyone.
v.34 says "for all the sins of the Israelites". Again, everyone.
I hope this satisfies your desire that I not ignore Lev 16. I'm still convinced that Christ's atonement is exactly what John said; for the sins of the whole world. Not just believers.
I think that you have to be careful here with your use of v. 33 as the verse states, 'and he shall make atonement for the priests and for all the people of the assembly' (ESV). It is limited to 'the people of the assembly' - all of them.
That does not negate the fact that 1 John 2:2 states that Jesus is 'the propitiation for our sins, and not for ours only but also for the sins of the whole world' (ESV).
This is clear that two groups of people are contrasted:
(1) 'Our sins' and thus referring to the Christians who is 2:1 are described as 'my little children' who when they sin 'have an advocate with the Father'. This is language that cannot apply to unbelievers 'an advocate'; and
(2) 'the sins of the whole world'.
If John meant this to be limited atonement to the elect only, point #2 would not be necessary as 'our sins' (of believers) would be totally adequate to confirm this.
However, the addition of 'the sins of the whole world' is clear indication that John did not want to teach limited atonement for the elect only. He went out of his way to refute such a view by his inclusion of two groups of people 'our sins' (the elect) and 'the sins of the whole world' (Jews and Gentiles of the non-elect - the rest of the world).
For these latter people, propitiation was only potential as their response was needed for actualising of their salvation through Christ's propitiation (appeasing the wrath of God).
Unlimited atonement is also taught in Hebrews 2:9, '.... so that by the grace of God he might taste death for
everyone' (ESV). It does not state, 'everyone of the elect'.
Oz