Very interesting. I have a feeling that it will often reach the max very quickly though.
Also, unupped table says max 9 but image says 7.
It should be 7, thanks for catching that.
1 lux will be worth 1 HP of healing/damage?
Yes, effectively. If used on its owner or opposing player, its akin to adding 1 DR to the shield (in terms of HP advantage) with a threshold of 7/9 per stack.
It can also be used to target creatures, so it has other applications.
I'm not sure what a good balance is in terms of damage / healing per lux (e.g. per shield action) so I went for the simplest scaling.
I'm open to changing it if needed, though it will be tricky to fit in the card.