Will I be CAP exempt with employer B (if it files H1B for me) if I leave employer A before H1B is approved.

No. One cannot seek to put the cart before the horse.

This question needs in all likelihood to be posed to a tribal lawyer.

Different start date on i129 and i797 due to multiple RFEs. Is this a probelm?

And don't forget that one is always at the mercy of an "AP" delay when undergoing visa interview in India.

How long do i have to wait to file for spouse ?

I wouldn't even bother with this gentleman - there is no way he is coming back to the USA anytime soon - if ever - once sentenced and removed.

How long will the second i-130 takes to be approved?

I agree with both my esteemed colleagues: "get a lawyer", otherwise risk seeing this deteriorate and take a very long time.

Am I barred from the United States?

Upon your departure you have triggered the 10 year inadmissibility bar.

Can beneficiary of a family 1st pref. petition(F1) get married the next day after admission in the US or it has wait 90 days ?

Yes, you can safely get married even after one day of having been admitted into the US.

If I have a forcible entry and detainer as a minor why does that effect me as an adult when applying for an apartment?

This is not an immigration law question/matter.

I live in Dallas, TX area. I have a pending i-485 (AOS), I am in need for emergency travel document for humanitarian purposes.

Don't try to do this alone - on your own you stand very little chance of success. Hire a reputable immigration lawyer to assist and prosecute this...

My employer did not get I797A/B, can my wife go for h4 stamping with I797C?

Isn't your employer's immigration attorney available to offer you guidance on this?