Can a non-profit buy a product (class preparation docs) from a person with J-2 visa who is waiting for the renewal of their EAD?

If you pay her for her product, instead of paying her salary, no law will be violated.

While I change my address online how do I know my address already changed?

You will receive notice from USCIS if that's what you are asking.

May the spouse of immigrant with approved I-140 form apply for green card together with him?

Yes, you can adjust status with your husband.

Can I do the above?

No, it is not legal for B1/B2 visa holder to conduct business in USA. In your case, your US company is the middle entity for the cross-border...

You shouldn't work in US in F1 Status hence you should hire somebody to carry out the transaction.

Attorney client retainer agreement Client agrees to pay for attorney services the summa $1500 of which 250 has been paid

You should ask your attorney about the reasons. Do all services you received fall into the scope of serve of the agreement or extra services are...

What can I do about this. Do I have any legal l rights

Who have you been dealing with? Who are supposed to repair it? There might be breach of contract but it depends on the specific terms. You should...

Am I bound legally and what should I do to ensure I am not in the wrong

I think you are right on insisting on the court paper.

Can I file a breach of contract, take them to court for the money I paid for the trailer. Not interested in owning it anymore.

Do you have a contract? What did you do when he died? How long ago was that? If there is a valid contract, you probably won't be able to get...

How long should I wait for filing her change of status? What is the process for that?

You don't have to wait at all. File change of status. If you are not sure what to do, how to do, hire an attorney.