I receive my reduced benefit of $720 at age 63. My ex receives 1200 in disability. If he passes away will I be able to Apply for 1200 in widower benefits if I have reached my full retirement age by then, even though I started receiving my own benefits early?

Hi,

Yes, but you would only receive the higher benefit rate, not that rate plus your own. Of course, this assumes that you meet the requirements for surviving divorced spousal benefits (https://www.ssa.gov/planners/survivors/ifyou3.html).

Best, Jerry