If I understand correctly, the fault was yours for not reading the agreement thoroughly so, no, you cannot prevail in a lawsuit IMO.

You can report it to the police who will decide whether to recommend charges to the DA, but don't get your hopes up.

How to find out if there's a warrant for me

This is likely a scam, asking you for money.

Of course it is. What else could they have done?

Can I sue him for not paying me back?

Easier to file with your insurance company but yes you can sue him.

Can I sue the motel if ?;

Unless you were harmed in some way (i.e. items stolen, assaulted, etc) there is nothing to sue for. Mistakes happen.

Is it illegal for my ex husband to make my kids sign a paper they didn’t understand/read?

While not illegal, I doubt it will have any impact in court.

Are there any identifying marks (phone number, SSN, etc) on the pictures? If not, so what?

I hope she called police on the punk. But you are asking a scientific question. I suspect DNA analysis can be done.

Can I sue Uber for Leaving me 3 months last year and 1 months this year without work for the same problem which they lied ?

A lawsuit will cost much more than you could potentially recover.