As others have commented above, "Immune to Fear" will depend largely on how you model Fear. If Fear was a defined type of PRE Attack (which is how I would do it), then its counter would be something like PRE, Defensive only (-1), Only vs Fear (-1 to -2). Buy as many points as you need to reduce most fear attacks to <10 points of effect.
Being unable to comprehend magic does not sound very limiting to me, especially in a low-to-moderate magic setting. While the character may not be able to use magic, he will generally have other options to compensate. I would consider it Infrequent, slightly limiting (10 pts).