I have an EB3 with PD of 03/2007 (ROW) with I-485 pending (more than 2 years),EAD, & AP.Due to retrogression,I am contemplating on starting a new EB2 application.I am a Software Engineer with 9 years of work experience,currently on H1B as well.Before joining my current employer, I had 5 years of work experience.My questions are:

1) Is EB2 application grim these days for Software Engineers?
2) Is it better to start an EB2 application with current or new employer?
3) If I move to a new employer, transfer my H1B, invoke AC21, can my current employer still revoke my I-140 which will cause denial of my current I-485?
4) Will a new EB2 application hurt my current EB3 application in any way?