The 2 Thessalonians is not applicable...
AMP
not to be quickly unsettled or alarmed either by a [so-called prophetic revelation of a] spirit or a message or a letter [alleged to be] from us, to the effect that the day of the Lord has [already] come.
Timothy and the other letters have nothing to do with "the Lord has already come". That is a very specific application on which letters he is referring to lest we say all of Paul's letters are fake.
I gave all the information before... no need to repeat.
WHOA THERE HORSEY!
It is the very claim you are making on the other side of the coin. "Modern scholars say" is an appeal to authority.
There is one letter mentioned in Corinthians that still hasn't been found. Time has a way of eradicating original document and that is why, so many times, we rely on quotes from people during that time-period. Thus we include the Pastoral epistles.
As I also mentioned: " The internal evidence certainly supports Paul as the author, especially references to his earlier life (
1Ti 1:13), and the close relationship between the author and Timothy"
This is definitely an appeal to ONE authority (as if he was the determinant of what was accepted and what wasn't). As I quoted before: "Early sources in church history that attribute this letter to Paul include: Eusebius (300 A.D.), Origen (250 A.D.), Clement of Alexandria (200 A.D.), Tertullian (200 A.D.), Irenaeus (200 A.D.), the Muratorian Fragment (180 A.D.). References to the epistle are also found in the writings of Theophilus of Antioch (180 A.D.), Justin Martyr (160 A.D.), Polycarp (135 A.D.), and Clement of Rome (90 A.D.)."
If we were to have taken the viewpoint of the "modern scholars" of Marcion's time... he would be outnumbered.
OBVIOUSLY.
The other epistles dealt with the church at large. These had to do with personal letters. The very nature of who it is addressed to dictates what verbiage is being used.
If I wrote a letter to the church vs. my daughter... don't you think it would be totally different?
Again, look to the above statement. Too say that the words "Hapax Legomena, and they are not actually attested in any other koine writings before the second century" and yet we have people quoting them before the second century make this statement irrelevant in my view. How can one say they didn't exist when people use them during that time?
Again.... the difference between talking to a church vs a son in the faith.
This will take more time to address... don't have the time right now.