Filing i751 jointly and separating after?

[cynpen 7]

Hi everybody! I should be filing form i 751 this October/November (my green card expires in January). I am in a real marriage with a US citizen but things have not really been working out. We had many issues (addiction related and other complicated stuff) but we manage to move past them and overcome those challenges. However, after all we have been through, we decided the best for us is to remain friends, but we are not interested in pursuing a romantic relationship right now. We agreed to stay together until I get the green card just to make things easier (and, besides, I am also getting my Italian citizenship and he wants it as well, so in the end it's like an exchange of citizenships :)). Nobody really knows we are planning on separating in the future and we live together (with his parents) and continue to behave and have all the things married couples have. There has been no separation or anything of the sort.
Not too long ago I found out that the processing time for the i 751 in Illinois is very long (18 to 20 months) and I am starting to doubt if we will make it to year 2020 (when I should be getting the green card) like this, living with his parents and continuing to pretend we are not thinking about separating. I think we both could do it, since we get along really well, but part of me wants to move on with my life.
I wanted to know about filing form i 751 jointly and then separating after a few months, but continuing to file jointly. Is this a good choice? I know I will be asked for a RFE and that most likely we will have to go to an interview. We are both fine with that and with going to the interview together, there would not be any issues. What kind of evidence does USCIS ask for in these cases (is it related to the beginning of the bona fide marriage, or do they ask for information on the separation, like for you to send evidence that you are going to couples therapy or something like that?). I have a lot of evidence of therapy but it is related to my husband's addiction and I am sure he does not want to disclose that to USCIS, since it is pretty private. Also, I have been reading that, when we separate, we should send a letter to USCIS telling them that we separated and that we still want to file jointly. Does any of you have a sample of that? Can it be sent at any time after filing jointly? What should it include? If we don't send the letter, how do I notify USCIS that we want to continue to file jointly? We would be telling them that we are on a trial separation but we do not want to get divorced at this point and that we are both willing to go to the interview together.

Our idea is to not get divorced until I get the green card and he gets the Italian citizenship, so we don't mind staying married for 3 more years or so (and we are on really good terms). I know he will come to the interview with me and that we can go through it and prove that our marriage is real without problems.
Any advice will be greatly appreciated Thank you very much!

[NikLR 13,227]

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