I do not understand how it will helps him if you agree to complete the immigration paperwork and then get divorced. You can always write a letter to the Immigration Court telling them what he is trying to do
Having a bona fide marriage with a US citizen should allow you to change status from student visa to that of conditional permanent resident if you and your spouse file the appropriate forms with USCIS. Timing will depend on where in the US you are. Should take approximately 6 months once your forms are filed and you should be allowed to remain in the US until a decision is made by USCIS on your adjustment of status application.
You need to be careful of her "intent"' entering the country on a tourist visa. This could later become an issue when you all apply for a green card based on marraige.
Best to call an attorney and discuss Fiance visa options and/or other options
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