What can I do to make sure he never does this to anyone again? What's the statute of limitation?

You waited too long for a sexual harassment complaint plus it sounds like you have no proof.

You need to hire an experienced lawyer and he or she can do a proper evaluation of your case.

How many people do I need to have to go forward with a class action lawsuit against a company.?

There is no general harassment in Illinois so it depends on what the harassment is. Also it depends o whether other people wish to come forward...

How did your bosses boss know? It is a little unclear from what you wrote what actually transpired.

Why my brother didn't get a autopsy or a death certificate?

You can ask the coroner for one. Contact them I am sure you can find their information online.

Will he be able to obtain his visa

He should discuss it with the attorney who is doing his immigration case. Best of luck.

You should contact a local attorney who can give you the best advice on that issue to protect your rights.

If they are disturbing the peace you can call the police.

I am looking for an apartment release form...

I agree with the answer above. Make sure you get a release too.

URGENT ADVISE - Previous I-140 Approved, PD is Current, New PERM Certified, Company not filing Concurrently?

You need to hire a local immigration attorney and make sure you get everything done properly.