I am interested in EB2NIW, would you please let me know my eligibility, process timeline, and cost.? i am outside USA?

You should contact 3 attorneys in private to have them evaluate your potential. Your questions are too complicated for a general information blog.

How?

Go and meet him. Then file a form I-129F to sponsor him as your fiance.

Do you have the money to pay 100% of her treatment expenses in the US? If so, have an attorney assist you with a B-2 medical treatment extension.

Paid Family Leave while waiting for OPT?

I agree with Mr. Smith ... since you won't have an EAD, you probably won't qualify for paid leave.

Can USC marry H2A worker when he comes back next yr w/o it being preconceived intent?

You would be better off filing for I-129F for a fiance visa.

Immigration

That could be a problem. BUT, there is an alternative ... get a computer printed Tax Return TRANSCRIPT from www.irs.gov ... they will keep her...

USCIS office visit after an international trip

I recommend option #3 ... change your travel plans.

I suggest that you: 1. Talk to an attorney about the 90 day rule 2. Keep in mind how soon your husband entered on H-1B 3. Discuss, when...

Don't waste your time looking at the processing time charts. As you can see ... they constantly change and are usually inaccurate. If I were to...

Can I stay in US without doing any job, if I apply for change of status to F2, within 90 days of OPT unemployment period?

Although you use the word 'rejected' (which is when CIS mails back the papers w/o processing them) I'll assume you mean 'denied'. Yes, there is...