If I buy a font from here, am I allowed to use it in files for print, then let the printer use it to process my file?? Along with embed them into a PDF?

The best answer you can possibly get: Depends on the license of the author.

I have noticed that. Looking at it, the reality of font management from a legal standpoint is virtually impossible.

Virtual is not the same as real, if I remember well ...

But you are one of the ones who with great care avoid telling us about which font/designer you are talking about. So this whole thread is thin air.

Why does it matter? Ok, these fonts.....

Font Bureau
Interstate Volume3
Interstate Volume 2

Fonts.com
FF Meta Serif/Sans OT Complete Suite
SketchBlock Family OpenType
InfoBits
Tahoma
Brisa
Miss LeGatees
Marydale Complete Family Pack

Monotype
LemonadeICG Complete Family Pack
Langer Complete Family Pack
AT Gothic Extra Light Extended

Skippy Sharpie
Eraser Dust
Democratica
Crackhouse
Script Collection Mac TTF, T1 (Postscript)

You can not buy commercial fonts at Dafont.

What does that mean. At least the last 5 are single, non-group, Fonts. Why does it seem like you are dodging the same question all the font developers are?

These fonts are from large foundries that does not sold their fonts here, on dafont.
and the 5 one at the end, i can't find them on dafont.
As Kat says, it depends on the font license. I would say yes to your question but can't answer for any font designer.
In my case, the lincensed version of my fonts authorize font embedding and the processing of your files by a printer (this printer have to delete font files once the job is done)