Convicted person would be a competent witness under Section 118 of the Indian Evidence Act. If a convicted person has the ability to understand the question put to him and to give its rational answer then he is a competent witness. His conviction does not bar him from becoming a witness of fact in a criminal trial if he has the personal knowledge of the relevant fact.
The maintenance order passed under section 125 of the code of criminal procedure is tentative in nature. The court may stay the maintenance order passed under section 125 crpc if wife already getting alimony under section 24 HMA.
Your boyfriend should have some evidence to prove mental harassment otherwise he cannot file any criminal case against you. A hypothesis cannot take the place of reality. Threatening on the basis of such a hypothesis is an offence of criminal intimidation. Thus your boyfriend cannot file a case on mental harassment.
Sexual intercourse on the false promise of marriage constitutes the offence of rape. The consent was not free if it was given due to misconception of fact. Thereby the person commits the offence of rape which is punishable under section 376 of the Indian Penal Code.