What did Morritz do at the end? Read this.

“I also keep stating over and over that when Moritz leaves the auction and the man in the street is calling after him to give him back his coat he appears PARANOID .... why ??? .... because he has the real violin and he thinks they are on to him. If he had the fake there would have been no reason to have portrayed him as frightened or reluctant to respond to the voice behind him.”

Yes. You do keep stating that over and over.
If he were paranoid, he’d be scanning all around, suspecting everyone around him.
Instead, we see someone who appears confused and distracted.
Keep in mind that Moritz has just tried to commit a crime of theft and fraud.
He hears someone calling, but WHO is calling him, and WHY are they calling?
Have they discovered his attempted crime?
Is he about to be arrested?
Is his career over?

He could be thinking: “Did they realize I almost stole it? That I tried to perpetrate a fraud?”
It isn’t as if they’re going to say: “Oh! Wait a minute…..he tried to steal it but changed his mind. Don’t bother going after him.”

“Earlier Evan is showing slides to Moritz and explaining what he was going to have to do to repair the violin. He mentions various things INCLUDING repairing the part that you mention. By the time the violin is on display one would assume all the repairs have been made.”

But Moritz tells Evans not to touch the violin (regarding repairs).
I/we don’t know that Evans eventually went ahead with the repairs.
And, if an antique instrument is perfectly playable ‘as-is’, you DO NOT repair it!
If it is intact and playable, you don’t refinish it, you don’t repair it…you play it.
With a centuries old – perfectly playable instrument, you can’t justify re-doing a repair.
You’d run the risk of doing more damage.
You could also wind up altering the tone of the instrument.
Yes, it is referred to as a hack repair, but it was a playable instrument.

“The purpose of the close up was not to show us where the damage was but to show us the tag (#72) in order to make us familiar with the IDEA of a tag and what it is there for (the tag is important to the drama that takes place later in the movie).”

No.
The close-up was not necessary to show us the tag.
The number 72 is evident before the close-up.
We did not need to see the tag at all.
We knew it was THE red violin because Mr. Ruselsky zeroed in on it.
The red violin is the last item to be auctioned, so a tag/violin connection is unnecessary.
Anyway, a tag/violin correlation is made at the auction.
The auctioneer announces it as “…lot 72, (wait for it) the so-called red violin..”

Again, Moritz hears the voice of this instrument as Mr. Ruselsky plays it.
(Unfortunately, Mr. Ruselsky does not.)
Like it or not, Ruselsky IS an accomplished musician.
He might not have heard the ‘voice’ of the red violin, but he DID make it sing.
Moritz’ reaction to Ruselsky’s playing is testament to this.
It is also obvious that Moritz LOVES and appreciates this instrument deeply.
But Moritz understands that such an instrument belongs to a musician.
It is an instrument that should be played and HEARD.
Who’s Moritz’ daughter?
Is she accomplished?
Does she even have talent?
Heck, does she even enjoy playing the violin????