I'm confused. Instead of increasing the base damage of various spells (which I think is what you're doing, maybe I misunderstood), wouldn't it make more sense just to have all spells do damage that is a function of your destruction level? E.g., so and so icebolt deals 2 * (destruction level) in damage? Or maybe a combo of destruction level AND character level, if that's what it takes to prevent it from getting useless at higher levels?
The problem with this is that it isn't possible with the current game code. We don't have the CK. We're all working in hexadecimal, and we can't write scripts. We're doing what we can do with the game code.

Penumbral - any chance you'd be able to PM me how you got the +% damage as an enchant working, regardless of the string? I've been unable to get that working, basing it off the AlchFortifyDestruction code. Whatever I do bugs out. The reason being that you can link a SPEL effect from a perk, so if you attach a SPEL to the novice destruction perk, with conditionals, you could apply a separate effect inside the SPEL with conditionals to apply on say, every 5 ranks of destruction magic. A couple minutes of c/p would make it easy enough. A scale of 1.03, or 3% every 5 levels, comes to 1.03^20, or about an 80% increase by the time you hit rank 100. Alternatively, take the percentage you want and use the 20th root power to get the amount per 5 levels.
To fix the strings, I believe what you need to do is create a new string inside GMST and link to it. Skyrim Viewer on the nexus can access the strings and look at them, but we can't edit them. So creating a new one to link to should work. The actual string works like 'Destruction Spells do
% more damage', or something like that.