No worries Janek.
As far as it concerns the Veteran World a good entry point is the WMA (World Athletics Association) site
and the EVAA (European Association)
and the results of the Champs in there.
I don't know if you know the Veteran world, but in Multi-events, results, from the IAAF table, are adjusted with a WMA table of coefficients for age groups. That's what you see as results.
Veteran championships started in the late 70ies so that there are not so many years of results.
As for the results by National federations, that is a bit more difficult although the good point is that they usually don't organise more than 1 or 2 Decathlon for season. But I don't know if you want to get into that detail.
Maybe you should also upload, even if it is available on the IAAF site, the IAAF conversion table, just to make this Decathlon portal more complete. It would also be nice to have a score builder (runtime converter of performance in scores) but that takes some time to build and I got the feeling you guys built this site as a passionate hobby, so don't bother if you time is a limited resources for you.
Anyway a huge well-done again, because you've built a very nice site.