H1-B transfer to new employer with I-140 Receipt Number

[awaitinggc]

May be this question has been asked multiple times, but I could not find good response for this common situation. Here is my situation

I have I-140 approved and I have my A-Number as well as I-140 receipt number. Though my employer is not ready to share I-797 Approval Notice for I-140. They say that it is against company policy to share this information.

Now my question here is that

1. If I want to port my Priority Date to new employer, what all documents would be sufficient for porting? Would A-Number and I-140 Receipt number be sufficient? I do not have any documentary proof of the same.

2. As I am closing towards 6 years of H1-B validity, would I get new H1-B after transfer valid till end of 6 years or would it be for another 3 years based on approved I-140 ?

3. My I-140 has been approved last week. Do I have to meet I-140 validity criteria of 180 day before transferring H1-B, so I could port my Priority Date based on approved I-140?

My situation is not very complicated besides the fact that I do not have I-797 approval notice for approved I-140. But I am trying to know my options here. Any help would be appreciated.