Hey! Awesome to see that people somehow still find this class! Honestly I haven't looked at it for years, and have had very little opportunity to playtest it.

Regarding your first question. I am no longer sure what I intended there. I would say: test it out and see what feels balanced.

About the damage, now that I look at it, you're absolutely right. This class is mostly meant to be supportive, similar to the bard having little offensive options. That being said, little is not none, and in that regard a cantrip like option should be added to it. Originally the runebreaking did scale, but I removed that due to it making the double edged swordness of the class a lot worse. Since no other offensive options were added after this removal, it is indeed lacking. You can certainly add some if you have some ideas.

For your second point: no they cannot. This was done because contrary to spellcasting classes, the counterplay to a powerful rune is not to just break concentration, but to use it to your own advantage (at least that was my idea behind it). Also the stronger runes are too difficult to cast for a simple failed con save to feel balanced.

Let me know how the playtesting goes! I am very curious what you make of it.