Thanks for the chance to help. I am an attorney with over 12 years military law
You CAN get 100% VA compensation (including IU or Individual Unemployability) and FERS disability retirement so long as you qualify for each independently
IU requires that you have a single rating of 60% or more, or combined rating of 70% with at least one disability rated at 40%. So you are short on IU...you would need to have your ratings increased on one or both of your rated conditions to qualify for IU.
But assuming you can qualify for IU, you could receive IU at the same time a you receive FERS disability retirement. But you have to qualify for that independently as well.
VA disability is tied to your service connected injuries.
FERS disability is tied to your USPS connected injuries.
If you have both (both military connected disability and USPS connected disability) you can draw income from both.
IU does have one more limitation. There is an "income cap"....if you receive IU you are limited to how much money you earn from employment. If you have "substantial employment" you will not qualify. If you have "marginal employment" you can qualify. Currently, the cap for marginal employment is approx $12K year.
But this cap is for income...disability retirement would not qualify as income, so the FERS disability would not impact IU receipt.
Please let me know if you have more questions...happy to assist if I can