How does this play into my GI BIll subsistence allowance?
you can choose to get paid the GI Bill subsistence rate instead of the Chapter 31 subsistence allowance rate. In most cases the GI Bill rate is higher. Your VRC can help you with this
how do I qualify for the rehab & employment benefits if I'm active duty?
You have to meet certain requirements.  Do you have a 20% or higher pre-discharge disability rating memorandum rating and will soon leave the military?