US Immigration from Cambodia

Hello everyone from visa journey.
I have a family of five and recently received immigrants visas from us embassy in Phnom Penh, Cambodia and we have paid for all the green card and everything.
but I have some problems and questions needed to clarify. Maybe someone here might be able to help me out.
the problem is basically about personal assets that my family owns in Cambodia. We have quite a huge amount of asset here in Cambodia including house, personal savings account and cash. And we need to bring almost all of them to the United States. But I heard there is tax to everything in the US. I don t know if all of our assets needed to be taxed as well or not? I did some research that in order to bring those assets to the United States, we must declare all of those assets to the government right after receiving the green card. What I do not understand is how do we declare all of those assets to the government? Is there any specific form for that? And after declaration, is it true that we are not needed to pay for the tax of those assets anymore? And later on in the upcoming year of our staying, if we receive more income from Cambodia (we rent our house), do all those income need to be taxed?

Above are my questions and problems. Hopefully, someone can help me out. Thanks in advance :)

I am getting married next week and just learned that it may take weeks to get the recorded marriage certificate mailed to me. This will put us beyond the 90 days. The officiant says he can take a photo of what he files at the courthouse (is that a file stamped non-recorded marriage certificate or something else)? But I am worried that it won't be sufficient to adjust status.

What should I do?

1. File for AoS before the 90 days expires with the photo of documentation he sends me and possibly/probably get an RFE?

2. Wait beyond the ninety days and file for AoS?

3. File for AoS within and then supplement that filing in a few weeks with a nice copy of the recorded marriage certificate?

Also, after we file for AoS, what paperwork should my fiancee carry with her to prove she is in the country legally?

Thanks

At the time of interview, I will be employed. But because I will not have sufficient employment history (gap year), I wish to use a joint sponsor. I m wondering if I can - after having worked for a while(and after fianc receives green card) - remove this joint sponsor. I can t find any threads relating to this and was wondering if anyone has done it or if there is even an official option.