If I perform vasectomy on myself would it be illegal
Take: No it is not illegal. But may be taken as ground under cruelty / fraud if done by a male partner. Law has already given liberty to female spouse to have sweet will to have children or not out of marriage if one particular State's HC Judgment to be re-visited (read down). But when it comes to husband (spouse) same gender neutral treatment one will not get from same Law is my prudent view.
Can I now after marriage, get converted to Islam and remarry?
Take: Hon’ble SC has already said a big NO on conversion in the name of marriage or re-marriage.
If she contests divorce fine, but can I convert to islam and remarry?
Take: She can not only file divorce - serious criminal charges but also will get huge alimony too. After marriage the reply is a big NO, one cannot convert and re-marry agains in a already subsisting marriage.
oh also can she adopt without my consent
Take: A wife could adopt a son to her husband but she could not do so during her husband's life time without his express consent.
If she has kids with someone else can i get divorce easily
Take: Before or during her marriage with you in reference to context, first clarify that?
PS:-
Ever thought on lines of half yearly live-in arrangement of economics and option of opting on legal surrogacy having unique legal DNA of yours at any time of live-in, till no Live-in Laws on cards in immediate future except in distress (relationship in nature of marriage is what distress reads here as; but same is contained if half-yearly live-in arrangements opted for) part with maintenance - no residence rights - property snatching - no dowry arrests - no mother-in-law troubles invited forever and no alimony rights to live-in female partner that is all if it ever comes to that bundled as???