Will I be granted a Blue Card in my situation ?

Hello all,

I just had a binding job offer(1 page signed doc containing salary, probation period, payed holidays, other benefits) from a IT company located on Frankfurt am Main. The company is Italian but it has a registered trademark in Germany.

I had applied for the National Visa for Blue Card at the German Embassy in my country with the following docs:
    1. Binding job offer (Original +2 copies).
    2. Bachelor Diploma in Computer Engineering (Original +2 copies and translated).
    3. Anabin proof printed of the H+ recognized diploma.
    5. two copies of the visa application.
    6. two copy of the passport.

The salary was 40,000 €/year and since I belong to MINT professions it is grater than the threshold salary of 39,624€/year for the 2017. But the visa was rejected by the immigration authority, they stated that the minimum salary should be 3,500 €/month or more that 42,000 €/year, and they were giving me a second change to bring a contract with a salary starting from 3,500 euro/month.

I have renegotiated the salary again and got another job offer letter with 42,000 euro/year (3,500 euro/month). I have updated the application at the German embassy with the new offer and I still am waiting for their response.

Unfortunately the company does not have prior experience with hiring non-eu citizens. So I am following my self all the process.

Now the situation is like this: The application from the embassy will be forwarded for approval to the immigration authority and to the federal employment agency(because for the MINT professions with salary under 50,800 euro/year it is required the approval from the ZAV). 10 days have passed since my application and still no response.

Now I am concerned. 

Is there any chance that the federal employment agency can reject my application?

How long does this process lasts (the approval from Auslanderbehorde and Federal Employment Agency) ?

Is it the job offer sufficient for the Auslanderbehorde  to give the approve or it is needed the full Employment Contract ?

Thank you in advance!