One thing you will need to watch out for and consider.
If you were to get a 30% rating, your overall statement would be
Occupational and social impairment with occasional decrease in work efficiency and intermittent periods of inability to perform occupational tasks (although generally functioning satisfactorily
If you were to get 50% rating, your overall statement would be
Occupational and social impairment with reduced reliability and productivity
The 70% rating is:
Occupational and social impairment, with deficiencies in most areas, such as work, school, family relations, judgment, thinking, or mood, due to such symptoms
If you were to get retired at 30% with your GI Bill with the intention to attend school, you might be building the case against yourself for continued benefits. Its hard to say you suffer from a mental health condition that prevents you from being successful in the world, and then go out into the world and be successful at school.
Keep in mine, I'm being retired for a mental health disorder, so these are things my treatment team and I have discussed, mainly about me getting healthy enough to get my PhD and return to my teaching career.