OP - Your compensation under EC 261/2004 is 75% of the base fare ticket cost FRA-JFK, e.g. no taxes & fees.
Put the GPU aside for a moment and call LH and ask how the EUR 1000 was calculated. LH is pretty good about those calculations, so it is likely OK. But, it is worth checking.
Turning to the GPU, as noted, LH doesn't deal in GPU's and can't return it. But, if UA asks, LH will detail the e-ticket activity. However, if LH authorizes the GPU release, that is a revenue loss to LH which is quite sticky about that.
You may well find that LH either balks or is willing to let the GPU go in return for the cash compensation. Unlikely that you will wind up with EUR 1,000 + GPU.