H1B 2016 approved petition expiring on Sep 2017 without stamping

I have a approved H1B petition(expiring on Sep 2017) and corresponding docs(hardcopy) handed over to me by my employer A(MNC).

My current employer is not approving for H1B VISA stamping because there are no current opening available in the project nor releasing from the project, so that i can find another project to do an amendment.

Please guide me in this regard,what are the best possible options available for me in the current scenario?

If i join another employer B, is there a possibility of transferring my H1B to the new employer and travel US from there? What are the possibility of Employer A rejecting the H1B transfer claim from Employer B(if that is possible)?

If i don’t travel to US within Sep 2017 from Employer A, am i eligible for cap exempt for my next H1B petition?