I got a letter from DALLAS service center today. It indicates that my case is under review of Adjudicator and I should receive a decision or notice of other action after 90-120 days from today. Is that a good sign?

not necessarily. It seems like there is some serious investigation going on and you could be risking a denial. You should get your case looked at now rather than waiting until the resolution.

What should I do? I make info pass next week to see them in person. Do I need to use the info pass to talk to them? Or I don't need to. Your sound make me so worry

you should get an attorney to look at all the documents you filed.

Then what they will do next. Fortunately, I am still in school with good status and if my case is denied I won't get any effect to my student status right.

Attached is the link show that all cases must be in the adjudication service. Is that true???
http://www.uscis.gov/ilink/docView/AFM/HTML/AFM/0-0-0-1/0-0-0-1067/0-0-0-1166.html