https://www.soundimmigration.com/i-864-enforcement/
If this does not scare you, well it should.
USCIS are not going to be interested unless you have SOLID evidence of immigration fraud, not marital issues.
I agree with the others divorce asap.
Paying for someone's education in the US suggests they must be pretty wealthy, we all know it is not cheap.
The Singapore guy, well it is 90 days and not $500, but please let us know how it goes when he try to reset his passport.
She is here on the VWP. No visa.
ESTA gets you on the plane and allows you to seek entry.
When adjusting from the VWP it is perhaps more important to file within the 90 days.
I have a preference for adjusting assuming all others things are equal but obviously do not know your details.