Scriptures and agrees they are a testimony of the many faithful covenant people over the millennia, which includes many of the Jews (which Paul says were enlightened ahead of the Gentiles for a time).

And even with that huge advantage (at the time), Jews don't become honest and nice tribe. And they didn't go that path consciously. Even lasy Greeks with all their old pagan shit was able to become leading Christian nation at some moment.

So despite the many infiltrations, our covenant runs right through Israel before it gets to all the nations.

It exactly "runs through" Israel, leaving no single drop in it, like water through PTFE tube.

Who knows, may be Jews was a God's test if He really give humans free will. If even God can't convince some tribe to behave one way or another, then they really have free will. The problem is that we now have to deal with the consequences of this God's experiment. And it is up to us completely.

The implication is that Jesus says true Ioudaious is a good thing.

Fulfilling promises is a good thing. Jews had to eternally obey commandments (be Judaists) in exchange for their salvation, but they didn't. They broke the deal and betrayed God. That was a bad thing. Following terms of deal, doing what you promised to do is a good thing.