How would changing job impact my GC process? (I-140 approved more than 180 days)


New Member
I have an approved I-140 more than couple of years and waiting for my priority date (EB-2) to be current. Recently, I have been offered a position (very similar role) in a new company, who is willing to file my H1B and GC (6 months from date of hire). I am trying to understand what are my options and how would it affect my GC process.
1. Can my current employer revoke my approved I-140? If so, should I ask my new employer to start GC right away?
2. My H1B visa will expire next year (April 2019). If the new I-140 isn't approved on time, Can I still extend my H1B
3. My wife is using H4EAD expiring this year Oct 2017. Will I be able to renew the H4EAD if my old I-140 is revoked and the new I-140 hasn't been filed or approved yet.

Thanks for your responses!