US Immigration from South Africa

I immigrated to the USA 3.5 years ago and my children stayed with their father abroad, I was going to settle for a year and then we would look at visitation. Before I left, my ex typed and we signed a maintenance agreement which was never filed at court, but he understood that it would take 6 months for me to be able to work and was gracious in that regard. When I arrived here, and looked at the job market I realized I would not be able to afford to pay him what I said I would (he typed the agreement up and said I must pay what he had been paying, but he had a corporate job and I have never had one). I kept in contact with him regarding this. AS soon as I got my green card COVID hit, and everything shut down. I was unable to find work until July last year (2021) and I sent him 25% of my income. I worked from home tutoring kids as that is what I have always done.
I am currently studying and my ex has refused to accept any money from me unless it is the amount he wants ($800pm). I can't send that, so I have opted to pay money to the kids school directly, which I have done all of this year.
Recently he got an attorney and said I owe a ton of backpay for the last 3.5 years, at the rate of $800.
There is no court doc stating what I should pay. He will not write a letter saying I have paid. I have all my proof of payments.
What on earth do I do for my application??

How do I fill in N-400 Part 9 if I'm filing after 3 years being married to a US citizen? It asks for total days outside USA in the last 5 years, but I have only been here 3.5 years.

Do I include the year and a half I was living abroad initially in my days?

Hello all,

We submitted the DS-160 for tourist visa for my boss in July 2022. His passport was stolen and has been issued with a new passport. We have paid the visa fees and have an appointment scheduled for December 6th, 2022. But I am worried because the DS_160 confirmation page as well as the visa fee receipt still shows old passport number. What should we do? Would they even let him inside the embassy if they notice this discrepancy? Any suggestion would be greatly appreciated.

I am applying for citizenship soon, as I married a US citizen.

Once I am a citizen, can I only apply for citizenship for my children under 18 who live abroad, if they were to live with me in the US? Or can I apply for citizenship for them while they live abroad?

My fiance (beneficiary) has a daughter from a previous marriage. We're working to gather the final documents now that we've received our NOA2. What if anything should we provide surrounding his child maintenance agreement that is in place?

We've tried various searches but can't find anything specific aside from stating we need notify the court of his intent to immigrate which we did before submitting the K1 Application.