Ok, I did some testing. Bolted brand new isofix anchor to IPE-beam, attached 1000 kg's to one unmodified loop and to modified=bent loop (one at a time as my "test rig" cannot lift 2000 kg's

).
Result: no matter is the loop bent or not, it will not brake and it seems that they behave similar to each other. So it will handle at least 2000 kg/33 kg = 60,6 G-forces and I still believe it is safe to attach my childrens to it.
Here are some pics also:

Assembly to IPE-beam

Bent loop at front and unmodified at back

Test rig

1000 kg's mass

Control lift with unmodified loop

And it is up

Unmodified loop after lift

Now with bent loop

And it is up also

Bent loop after lift

This is the only situation I want to see isofix anchor looking like this..

Same from side

Unmodified loop

Unmodified loop

Bent loop (that paint is peeling off, not metal cracking)

Bent loop (same here, only paint peeling off)
Edit. Resized some pics.
I did not have time to scrape those paints off, I might do that later to check is there any hidden cracks under the paint.