EB3. Jul2007' filer 140 approved 485 pending. on EAD. RN in a hospital.

while waiting my GC, I am thinking to take some classess parttime to prepare my future DNP prpgram @ university of mn. I am working .8 FTE so I would keep the hours while i do that. that way also I can get an advantage of tuition assist from my employer. questions here.
1) am I safe to do that pending AOS?
as far as I know, it is no problem as long as employer would offer a full-time job when 485 approved. So,I don't even need worry about it as long as I keep my work agreement that I started with? right?
2) how the school would consider me as? F-1 so SEVIS should know or same as green card holder. my guess is CIS would not even know my schoolin right?
3) plz tell me which regulation you referring to?