I am not judging you or anything, want to guide you in right direction...
Dowry 498(a) is classified under Indictable Offence (serious offence), which means it carried a possibility of heavy punishment, if the FIR is registered no matter what you will not be able to get a Positive Police Clarence from PSK, also PSK in India endorse and place a Stamp on your Passport (this could be Positive or Negative)
Point
1) You cannot apply for PR for your sister, her husband or herself should get eligible with Education/Work Exp and apply for themselve
2) You are doing this to save your sister, believe me if you have not committed any "Dowry crime" which is the case about, Court and Law will take time, cross check all the Witnesses, Proofs and you and your family will be Acquitted (Hire a good Lawyer, be fair with your case, dont bride people which is un-necessary, indian law and judicial system is fair and will acquit you and your family of all charges if you in real have not commited that crime), yes it will take 3 yrs from FIR day.....(This time will also go , do not worry)
3) To send your sister abroad on any Visa is unnecessary at this point of time, you should support each other , stay together and stay united till you all get acquitted ( as per you, your wife /her family did not gave you Dowry/money nor they have proof of it, in case if they have solid proofs and witnesses, then things will get difficult for you), if they have filed a fake dowry case ,court will reject there charge sheet after cross- examining each aspect , proofs and witnesses. Trust me on this fake acquisitions will get rejected during argument session in court, that's why lawyers and judges work for.
4) I would advise, till next 3 years don't look for any immigration or look to run away from a this case, fight back legally, you will Win if you did not commit your crime, judicial system is slow but fair, have trust on it.