I assume he is not CSRS or CSRS offset. You would receive the higher of the two Social Security benefits if you were full retirement age, probably age 66. If you receive widow's benefits before full retirement age, there would be a permanent reduction. Timing the filing for your widow's claim may be important.

Whether you are receiving SSDI or RSI, the computation is the same. You always receive your own benefit first. Then if you can get a higher benefit as a spouse or widow, you get the difference.

I don't think your widow's benefit would be subject to GPO (a reduction in your spousal benefits by a percentage of your government pension) because you are CSRS offset. Otherwise it would be.

Too much to figure in this forum.