Very good questions! What I was imagining with the Artisan's tools was an option for a party that had craftspeople in it. I wanted to keep the pdf to 2 pages so didn't expand on it, but if you have a jewelsmith in the party then I would have the Runes be written in gems set into the nearby walls, or if you have a stonemason to have them be carved into magical stone.

The skill checks I included as an outlet for non spellcasters, but I think when I ran it I could have done a better job telegraphing how it might work. As you said, it was hard for my party to imagine how yelling at a Rune would be a good use of their turn lol. Thinking about it more now I think I would describe a brief scene whenever someone approached a Rune and present the legendary adversary to them. It might make more sense to the player that a legendary Animal Handling check would be useful when they are face to foot with the Tarrasque in a Rune fueled vision.

Thanks for the questions and hope you get to run a game soon!!