PERM Audit & employer change (with approved I-140)

[crazyim5]

Hello folks, 

Before I explain my situation, let's call 

* previous employer = employer A
* current employer   = employer B
* future employer     = employer C

I recently got the news from lawyers at my current employer that my PERM has been put under audit by USCIS and the lawyers seem to believe it was a random lottery audit and they are filing a response this week. As the audit takes longer to process, it could take another 6 months before I get a decision (they applied for PERM in January 2021)
On the another hand, I have I-140 approved back in 2015 on EB2 (stood approved for 6 months and still stands approved as my previous employer A never revoked it). My country of birth is India.
Also, my current leg of H-1B visa expires in 10 months on June 2022.

Now, I'm close to getting a job offer from a different employer C and I suspect they would want me to join as soon as the visa transfer (aka new H-1B petition is complete which could be shorter than 6 months, especially if done with premium processing)

Here are my questions pertaining to joining employer C (I cannot ask these questions directly to my company lawyers for obvious reasons). Here goes:

1) Could I apply for further H-1B extensions with employer C based on the approved I-140 I have via employer A? 
2) What are the consequences of changing jobs in the middle of a PERM audit? What would go into my file at USCIS?
3) Would I get to keep the original Priority Date (PD) of 2015 when I apply for green card again via employer C in the future?
4) Would my experience (and skillsets attained) at employer B count towards my DOL prevailing wage (so called Notice of Job Opportunity) when I apply for it in the future via employer C?
5) How much of an impact would previous wage levels have in the outcome of the prevailing wage. I was on level 2 for SOC 15-1133 that went into the application employer A filed which eventually got me I-140 approved (back in 2015). But in the prevailing wage employer B filed earlier this year, it was level 4 and I'm expecting it would be level 4 or higher with employer C as well. I ask this question in the first place because it has been several years since I first filed prevailing wage with employer A and I have grown in my career since then and I want my immigration papers to reflect that.

Thanks a ton in advance!