If a couple decided to get married and one of them is a non US citizen on a visitor's visa for six months, when is it too late?

Are you a U.S. citizen? If you are, you can sponsor your spouse.

Will I be qualified for deferred action?

I agree with my colleague.

Quick question about value of assets on i-765worksheet..

I agree with my colleague.

Deferred Action 5 yr presence requirement - Does that mean I need to prove month-by-month or enough evidence in between months?

The form instruction explains how you can prove the requirement.

My brother I 485 was denied 2007, can he re apply his denied green card using his approved I 140 with current priority date?

Looks like your brother has been out of status for a while. He won't be able to adjust his status unless his 485 is based on the marriage to a...

Do I need a waiver if I am here on a J-visa and I am marrying a US citizen?

You can file your waiver application from here. (https://j1visawaiverrecommendation.state.gov/)

Is it mandatory to have 1 full year of outside US experience as manager to qualify for EB-1?

I agree with my colleague.

I agree with my colleague.

If I get approved for deferred action and then my husband petitions for me to get my green card can i avoid having to leave.

You still have to leave the U.S. to file a waiver application at the U.S. Consulate even if USCIS approve your deferred action application.

Extending my H1B and filing for Green Card. Will I have enough time?

I agree with my colleague. Please check your I-94 to make sure when your H-1B status expire. You need the valid H-1B visa to enter the U.S.