The key here is to find if the degree is accredited. Get together with the school.
EB2 Green Card
The job must also require (genuinely) EB-2 level qualifications.
There are some variables. Generally speaking, if the BTech is supposed to be a 4-year degree and you got it in three because of your diploma, you should be fine.
The biggest delay for most people is in the priority date movement. Check out the Visa Bulletin and the PERM processing times. That should give you a good idea.
Impossible to predict. It all depends upon the type of degrees and the language used in the Form ETA 9089
Cross changeability is possible if your spouse was born in a country other than your country of birth. She can file her I-485 only if she is in USA.
It is unlikely, but possible.
As long as the job requires a Master's degree and you have earned that degree by the time you file your PERM, you should be able to get EB-2.
Generally speaking, I see this as a good opportunity to start a new PERM under EB2 and then transfer the priority date. Speak with your lawyers.
I think your worry is well founded. These type of cases are difficult to get approved. I am commenting in general because I do not know the exact facts. Discuss your concern with your lawyers and if possible, get a response in writing.