Update! Extracting into a subfolder named telebeacon seems to be working now, tho I would swear I had already done that...

With it working, it's an amazing and balanced data pack that really makes killing Withers something to be willing to do... At least more than once or twice.
The effects are a very good idea, they do really make sense, giving teleportation some mechanics to take into account every time you plan a connection or even a jump, rather than just an unconsequencial, set and forget /tp that many other mod teleporters are. The fact that you can also set up a temporary portal anywhere with two occupied inventory spaces, that can bring you home and even back, makes exploration something both easier and more interesting, too. And the relatively limited number of portals, especially quality portals, you can set up, makes for some interesting choices, too. I have a couple suggestions, tho.
I'd love if the adverse effects were applied after you teleport, so that just accidentally getting in the beam of a paired beacon isn't deadly, or annoying if it's higher quality.
And, the link level (the materials of the pyramid) seems to be determined by the bottom most central block, meaning that a whole level 4 iron pyramid with a single emerald block in that position would count as a whole emerald pyramid. I understand that checking for more blocks would be more troublesome, but just so you know and perhaps can find an alternative.
Diamond and favourite for you, Sir!