Form I-140

I had applied for the compelling circumstances EAD as i140 beneficiary when I lost my H1 job past July from info. thru these calls and our discussion. I found a new H1 job eventually in the grace period that H1 got approved later in Dec 2020.

Now after long wait, USCIS sent me biometrics appt. letter to go to ASC for fingerprints for this EAD. My question-

1. Since it appears USCIS wants to proceed with this compelling EAD despite the fact they have approved H1 in Dec. itself, should I go for biometrics to get this EAD?
2. If yes, is it fine to work elsewhere using that EAD(may be part time) while maintaining my H1 status thru current H1 job, or I got to pick one of the two? leaving my current H1 job will make me ineligible for i485 filing (in case my priority date may become current in another year) as that EAD is no H1 status right?
3. Or should I not go for this EAD/biometrics at this point at all? do I need to inform USCIS anything?

Previously I was on H1B when my I-140 was approved. Currently I am on H4 status, not employed and my priority date became current.
Previous employer has provided Supplement J and I have filed I-485, I-765, I-131 concurrently. The Supplement J indicates (#9 in Part 6) I am not currently employed with the sponsoring employer.

Q1) Upon receiving AOS EAD, can I directly join a new employer after 180 days of pending I-485 if sponsoring employer doesn't have any open position?

Q2) Can I start searching for new job before 180 days of pending I-485, but join after 180 days? Or, I must have to start searching and interviewing for new job, only after 180 days?

Q3) At the time of filing AOS, my Supplement J indicated that I am not currently employed with the sponsoring employer. If I join the sponsoring employer upon receiving EAD, then do I have to send USCIS new Supplement J indicating that I am now employed with the sponsoring employer, knowing that it might take a decade for my Final Action Date to become current and I may not be employed with the sponsoring employer at the time of GC interview?

Q4) What if I need to change my employer after GC interview, but before receiving GC?

Q5) I heard, after 180 days of pending I-485, even if I change my job couple of times, I can take the Supplement J only from the employer with whom I will be working at the time of GC interview. But can I still send new Supplement J to USCIS from each employers everytime I change my job? Is that legally allowed? or, is there any concern? Because, it might take a decade for my Final Action Date to become current and within that timeframe I might have to change job 2-3 times.