Thanks for replying! Setting Hidden Power's damage to 60 definitely seems like the best thing to do, seeing as all the other attacks are adjusted to their gen VI stats. Shame about Moonblast, although have you tried looking at Mist Ball (signature move of Latias) for the precedent? I know nothing about making ROMs but it's similar to Moonblast in that it's a special attack with a chance (in this case 5%) to lower special attack, so I'm guessing you could try and copy the relevant information of that? Just don't forget that Moonblast's chance is 30% and not 5%, although if it's too difficult to create a new percentage then 5% would still be better than nothing.
Thanks again for making this ROM! :)