I was also on J-1 and other non-immigrant visa. The immigration lawyer who worked with me stressed the importance of maintaining my non-immigrant status. As far as I could tell, filing for adjustment in itself wasn't considered a violation, strictly speaking. Otherwise the answer to question about violating status would have been "yes" by merely filing I-485.
This was answered as "no" on forms. I successfully adjusted, successfully removed conditions and successfully became a citizen. It was never questioned.
Because I was on work visa with original employer, I never used EAD for employment. After I got GC, I updated I-9 with that document.