these following are your allegations against your husband and in-laws:
1. he faked about his educational qualifications.
2. he concealed his employment status.
3. mother-in-law asking your salary (you did not say whether it was entire salary or a portion of it)
4. your brother-in-law is misbehaving with you.
despite all these things, the affection level between you and your husband is normal and healthy level, my advise is just ignore all these things and get separate accomodation and shift far away from in-laws and especially from brother-in-law. if the relationship between the spouses is not healthy and affectionate one, then the question comes to that WHAT DO YOU WANT? Do you want annulment decree or divorce or judicial separation?
1. There are some cases, where court held that concealing the educational qualification and employment status from the spouse at the time of marriage for the purpose of solemnization of marriage is a material fact and it comes within the purview of "fraud" and the aggrieved spouse is entitled to the annulment decree. but in your case, as you have 5 months old child is there, the courts may incline to try to reconcile the differences, if both the spouses are in good financial conditions.
2. Regarding the third allegation, if the mother-in-law is asking the part of your salary for meeting your food and lodging bills, that is reasonable. If she is asking the whole amount curtailing your financial freedom, it is economic abuse and also cruelty.
3. The allegation is a very strong one and despite your complaint about him, if your husband and inlaws are not taking any action, it is nothing but utmost cruelty perpetrated against the wife.
On the basis of allegations, you can file a case for annulment of marriage under Section 12 (1)(c) under the ground of fraud or file a divorce case under Section 13 (1)(ia) under the ground of cruelty. If you want to keep the marriage relationship intact and avoid the problems, you can ask your husband for separate house for three of you. If he refuses, but you want to keep matrimonial relationship, then you have the relief under domestic violence Act seeking the shared household on the ground of economic abuse from mother-in-law and s*xual abuse from brother-in-law.