You can file for a divorce under the Hindu Marriage Act on the ground of adultery (Section 13( 1) of the Hindu marriage Act), desertion for a period more than three years (Section 13(1) (ib) of the Hindu Marriage Act, Case - Iachman Utamcha1vd Kirpalani v. Meena Alias Mota reported in AIR 1964 SC 40) or cruelty as your wife has left you and is living with another man ( Section 13 ( 1) (ia) of the Hindu Marriage Act . If the Court is satisfied that your claims are correct it will grant the divorce. With regard to the alimony, the Court will consider your financial condition and your wife’s financial condition before determining the amount under Section 27 of the Hindu Marriage Act. If you are able to establish that your wife is already married to another man then the Court may take that into consideration before deciding on the amount. She will not be entitled to any maintenance under Section 125 of the Code of Criminal Procedure as she is maintaining relationship with another man (M.Chinna Karuppasamy v. Kanimozhi, CRL.RC.(MD)No.142 of 2012)
With regard to section 498A of the Indian Penal Code, the Courts are quite cautious of the misuse of the provision and if your wife does not have any substantial proof to prove Section 498A against you, the matter will be dismissed by the Court. In the possible scenario that she has some evidence to show that you subjected her to cruelty while she was living with you, then the current presence of the boyfriend will have no consequence and you will be charged on the basis of the evidence produced before the Court.