increase the base power of light magic, or increase thani's MT to 9 or 10 so that micaiah doesn't chronically fall short of OHKOing the targets that thani is supposed to be effective against.you at least did this with a substantial improvement, congratulations. this stops her from being OHKO'd as early as chapter 1-1. increase micaiah's base HP and def by 2 points each or more.there are many ways to address these problems, very few of which you use. Micaiah has a lot of big problems, namely being slow, unable to take a hit, and not even strong offensively since light magic is weak. that's not meaningful at all, since micaiah is still dying more than 80% of the time in the earlygame. what is giving micaiah innate miracle going to do? instead of micaiah always dying, she now has a (100 - luk)% of dying. a ton of small changes like the one that you listed in the OP isn't going to adequately address FE10's problems. What FE10 needs is more playable chapters for some of the units who have little availability.
My attitude towards this is the same as my attitude towards FE6 improvement attempts, which is that FE10 is not in dire need of improvement and even if it were, i wouldn't trust a random user to make meaningful changes that have an impact on gameplay.