First of all "Up to that time the Spirit had not been given, since Jesus had not yet been glorified." John 7:39
Not true. This only applied to the disciples and not all believers in the past.
John the Baptist had the Spirit since the womb (Luke 1:15, and Luke 1:41).
1 Peter 1:10-11 says the Spirit of Christ was in the prophets.
10 "Of which salvation the prophets have inquired and searched diligently, who prophesied of the grace
that should come unto you:
11 Searching what, or what manner of time the Spirit of Christ which was in them did signify, when it testified beforehand the sufferings of Christ, and the glory that should follow."
(1 Peter 1:10-11).
Also, David says to God in Psalm 51 not to take His Holy Spirit from Him.
You said:
The New Covenant was not in effect until Acts chapter 2.
Again, not true. The testament was not in force until after the testator (Jesus) died.
16 "For where a testament
is, there must also of necessity be the death of the testator.
17 For a testament
is of force after men are dead: otherwise it is of no strength at all while the testator liveth." (Hebrews 9:16-17).
I mean, why do you think the temple veil was torn from top to bottom when Jesus died?
It's because the laws on the animal sacrifices were no longer acceptable and Christ's sacrifice began a New Covenant or a New Testament. There are many other verses that I could go into on this, but this should suffice to show you.
You said:
So while David and Abraham were justified by faith apart from works (which Paul explicitly states in Romans 4), they were not "Christians".
They might not have been called Christians, but unconfessed grievous sin had always caused a separation between God and man. For Adam brought death by his one time sin. Eve was deceived the devil's lie that she could break God's command and not die. This same lie is being pushed by the devil today.
You said:
They were not born of God.
Not true. Galatians 4:29 says that Isaac was born of the Spirit.
28 "Now
we, brethren,
as Isaac was, are
children of promise.
29 But as then he that was born after the flesh persecuted him that was
born after the Spirit, so also it is now." (Galatians 4:28-29).
You said:
So their behavior cannot be compare to those of us who have been born of God (Wesley makes that error), as described in 1John 3:9 "No one who is born of God will continue to sin, because God’s seed remains in him; he cannot go on sinning, because he has been born of God."
Modern Translations will say practice sin or continue in sin in 1 John 3:9 (as if to say it is talking exclusively of practicing sin), but this is not the case in the trusted KJV (that existed hundreds of years long before the Modern Translations showed up). (Note: I am not denying that it can be in reference to habitual sin, but it is not exclusively referring to habitual sin but also singular or temporary sin, too.).
The key to understanding 1 John 3:9 is realizing that this "does not commit sin" is in context to the gnostic belief who think sin does not exist or that sin is an illusion in some way (See 1 John 1:8 and 1 John 2:26). Christian Scientists today think sin is an illusion. OSAS proponents think future sin is forgiven them. So while they believe sin may exist on a physical level, they do not think sin exists for them on a spiritual level because they believe Jesus paid for their future sins (When the Bible never says future sin is forgiven us).
In other words,
1 John 3:6, and
1 John 3:9 is in view of "willful sin" or "justifying sin" in some way.
1 John 3:9 should read like this:
"Whosoever is born of God doth not commit sin
[willfully, as if to justify it]; for his seed remaineth in him: and he cannot sin
[willfully], because he is born of God."
1 John 3:6 should read like this:
"Whosoever abideth in him sinneth not
[willfully, seeking to justify their sin]: whosoever sinneth
[as if to justify their sin] hath not seen him, neither known him."
This would be in view or light of applying the context of the false gnostic belief that John warned the brethren about in 1 John 1:8.
Hebrews 10:26 ties this together. It says:
"For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins," (Hebrews 10:26).
Meaning, a person who sets out with the mindset that they are going to sin again, or that they are always going to be in a state of sin of some kind (Thereby justifying that they are going to willfully sin again) is going against 1 John 3:6, and 1 John 3:9.
You said:
In David's situation it simply states 2Sa 12:13 Then David said to Nathan, "I have sinned against the LORD." Nathan replied, "The LORD has taken away your sin. You are not going to die." No conditions mentioned.
In light of Psalms 51 (which was a confession of David afterwards), he asks for his sins to be forgiven.
So why would he seek forgiveness with the Lord if he understood Nathan as saying that his sins were forgiven on a spiritual level? It makes no sense. So obviously Nathan was referring to his sin being taken away in relation to his physical punishment or destruction. David would not die, but his son would die instead. This does not mean David did not feel like he did not have to seek forgiveness with the Lord over his sins so as to receive forgiveness.