Currently working in US with I140 approved through employer A just 1 month before 6 years on H1.
Now got H1 extension 3 years approved.
Got a good offer with employer B and I have decided to switch, I do have a copy of current employer's I140 and I797 approval.
Employer B won't file labor, I140 for next 12-15 months.
Current Visa stamping on passport expired almost 2 years ago.
I have to travel to India this year end which will be approx 3 months with employer B by then.

1) Visa stamping will be a problem with just about 3 months on payroll with employer B ?
2) Does my 140 need to be active for Visa Stamping as employer-A may revoke as soon as I change job ?
3) 3 year H1 will be invalidated as soon as employer A revokes I140 since the extension was based on that 140 ?