Don’t take rash decisions especially if you have kids. If you fear/know that a false 498a complaint is going to be put on you or if they threaten you in anyway it is better to be safe than sorry:-
1. Immediately file RCR, if your wife is separated from you (Restitution of Conjugal rights is like saying"I want my wife back(who deserted me), but with the following conditions"- but since the wife's intention itself is wrong, she won't be able to agree to those conditions(you can even make the conditions more difficult and impossible, to make sure that she will not come back).
2. File a police complaint mentioning Blackmail/extortion threat , threat for false dowry case , or any other thing you have the evidence for. Do not forget to mention that she had left the matrimonial home after taking all jewellery and cash in your absence, as the case may be.
3. Recording all the conversation if any(telephone recording devices, or miniature recording devices when in person discussions happen).
4. File a criminal case in court under 156(3)Cr.P.C under read Section 200 Cr.P.C, with reference to police complaint .(these are sections in the Code of Criminal procedure(Cr.P.C in short), 1973, reproduced alongside:
Section156 Cr.P.C - Police officer's power to investigate cognizable case
(1) Any officer in charge of a police station may, without the order of a Magistrate, investigate any cognizable case which a Court having jurisdiction over the local area within the limits of such station would have power to inquire into or try under the provisions of Chapter XIII.
(2) No proceeding of a police officer in any such case shall at any stage be called in question on the ground that the case was one which such officer was not empowered under this section to investigate.
(3) Any Magistrate empowered under Section 190 Cr.P.C may order such an investigation as above-mentioned.
Section 200 Cr.P.C - Examination of complainant
A
Magistrate taking cognizance of an offence on complaint shall examine upon oath
the complainant and the witnesses present, if any, and the substance of such
examination shall be reduced to writing and shall be signed by the complainant
and the witnesses, and also by the Magistrate:
Provided that, when the complaint is made in writing, the Magistrate need not examine the complainant and the witnesses-
(a) if a public servant acting or purporting to act in the discharge of his official duties or a Court has made the complaint; or(b) if the Magistrate makes over the case for inquiry or trial to another Magistrate under Section 192 Cr.P.C:
Provided further that if the Magistrate makes over the case to another Magistrate under Section 192 Cr.P.C after examining the complainant and the witnesses, the latter Magistrate need not re-examine them.
Provided that, when the complaint is made in writing, the Magistrate need not examine the complainant and the witnesses-
(a) if a public servant acting or purporting to act in the discharge of his official duties or a Court has made the complaint; or(b) if the Magistrate makes over the case for inquiry or trial to another Magistrate under Section 192 Cr.P.C:
Provided further that if the Magistrate makes over the case to another Magistrate under Section 192 Cr.P.C after examining the complainant and the witnesses, the latter Magistrate need not re-examine them.
5. Take the certified copy from court and keep it with you . Make a couple of copies. Send it to nearest police station. Nearest police station of your in-laws. File for Anticipatory bail in the High Court.
If the police insist you come to police station or come to your place for arrest after they have been bribed sufficiently by your wife or in-laws, just submit the court petition. They are the criminals , not you.