Good questions.
I finished my interview 3 weeks ago and this very issue came up - about how long I was with the co. that sponsored my GC, when I left (exact dates), why I left, etc. I was pretty scared, but in the end, I was recommended for approval and passed the interview.
The strange thing is that I have owned (and been employed by) my own co. since 2000 and in the n400, they only want 5 yr. emp. history. So, even though I only listed MyCo. in that section, the IO started
writing down my previous emp. hist. with the sponsoring GC co. and prior in red ink right under the sect. where I wrote my 5 yr. history..... she even kept asking me to give the EXACT date I left the sponsoring co. (which was about 5 months after getting my GC). I also had to show a bunch of other docs. - luckily I had it all with me except W2's from 8 yrs.ago -
which she asked for!!
Not to scare you, but in your case, I think that's going to be a big issue -because the red flag that goes off for them is that this was not a legitimate marriage betw. you and the emp. Then the issue of tax returns comes up (which BTW, I was asked to show). Ofcourse, if you have proof - like a termination letter or whatever, then you might be fine. They have a list of some black listed companies from the IRS that my IO was looking through - I think they were mostly Indian consulting firms that have a history or are under IRS/CIS watch for fraudulent employment/immigration issues. The IO even told me that later in my interview when we were making some light conversation
Also understand that some of the questioning and
how deep they want to dig depends totally on the IO/DAO, but in most case like yours & mine, GC-through-employment is pretty standard and they have a set list of questions to ask. One thing to remember is to never lie about anything. Never, never, never. They have all your history on file - from the very day you made contact with the USCIS or set foot on U.S. soil. The only stuff that they *might* not have in front of them during the interview is your IRS files, but even then, IO told me (kind of winking and smiling) that they could
"easily get it" if they want to double check. So, again, if they get the feeling you are pulling the wool over their eyes, they'll probably put your interview in pending and ask you to send documentation (tax returns, W2's, etc.) and then ofcourse they'll double check it.
I hope I didn't scare you - just telling you what I went through and what I think would have happened had I not been truthful and/or shown all docs.