I have a few questions regarding green card processing prior to joining the sponsoring employer and I have tried to explain my issue below.I am very sorry if the content is very elaborate or confusing.

My current employer has been working on my PERM case for the last 8 months and just started off with the advertising and job recruitment process.I am on my 5th year of the H1B and my 6 years of H1 gets over by 5-Dec-2017.My current employer is in the services industry but has been going through a rough phase with losses for the past few years and it is a big question if they could last until end of the next year.I was told by my current employer that my PERM would be filed only by the end of Jan 2017 (next year) as the earliest.The problem I am facing is, if there would be an audit on my PERM, it could totally jeopardize my H1 and Green Card status, since it seems to take around 8-9 month for the audited case to be approved and I am not sure my employer could last until the end of the year due the financial troubles currently it is facing, but it certainly can last until next summer.

Recently, I was approached by a staffing firm (who has a considerable number of clients and IT team in the city i live), for my skillset and experience and mentioned that they should be able to take care of this issue by filing for my PERM 365 days prior to my 6 years of H1 completion.The approach they mentioned is to make use of the prevailing wage and advertising/job recruitment process they have been processing on for another employee in a similar skillset and experience as mine, who joined a few months ago and file for my PERM soon after I join their firm with an H1 transfer.They affirmed they should be able to file for the PERM by mid Nov, if I were to accept their offer of employment in the next couple of weeks.The questions I have are

1. Can a Green card process started prior to joining the sponsoring employer, similar to my case ?
2. Can a prevailing wage and job advertising/recruitment process be used simultaneously for 2 candidates for the PERM processing ?
3. Can the PERM audited solely because of either or both of the above two reasons ?
4. The salary I have been offered is 10K less, but has better bonus and benefits, which I find on par with my current employment.Would this 10K reduction in salary affect my immigration process (H1 transfer, GC or visa stamping) ?

Thank you very much and appreciate the time taken to looking in to my question