I am 63. Can I apply for my reduced benefits now and then when my ex dies apply for divorced widow benefits? Would I receive his full amount if he was on disability at the time of death?
Possibly. You can file for reduced benefits on your own account now, but there is an earnings test that may limit the benefits that you could receive prior to full retirement age (https://www.ssa.gov/planners/retire/whileworking2.html). Of course, if you aren't working, you won't have to worry about that. You may also be eligible for an excess divorced spousal benefit while your ex-husband is living if his disability rate is more than twice as much as your full retirement age rate, and if you were married for at least 10 years.
Then, assuming that you were married for at least 10 years, you could file for surviving divorced spousal benefits on your ex-husband's record if he dies before you. If he's receiving Social Security disability benefits, that would be roughly the amount that you could draw in the event of his death, if you are at least age 66 when the death occurs. If he dies before then, your surviving divorced spousal benefits would be reduced if you start them prior to age 66. And, just to clarify, you couldn't receive both your own benefit and his in full, just roughly the higher of the two benefits.