1. She can ask for alimony, but a number of High Courts have ruled that adultery is unchaste behaviour and disentitles her to the relief of alimony and maintenance as per Section 25(3) of the Hindu Marriage Act. (Here’s a recent judgement of the Calcutta High Court: http://judis.nic.in/Judis_Kolkata/All/list_new2_v1.asp?Jud_Pdf_Name=FMA_322_2016_31072018_J_87_273.pdf&Court_Id=2)
You will first need to obtain a decree of divorce based on her alleged adulterous lifestyle. Suffice it to say you will need a competent lawyer to make and present your case.
2. It could take quite a while that can drag on for years together. I would not want to put a number on this torturous tedium.
3. No, you cannot force her.
4. An MOU or Settlement Deed notwithstanding, no party to a marriage can be compelled to lend his or her assent to a mutual-consent divorce. Was there a settlement to this effect pursuant to the orders of a Court? Because in that case she would be guilty of contempt of court.
5. You can indeed proceed on both those grounds. The fact that she has backed out of the mutual-consent divorce with a view to harassing you also constitutes mental harassment.