This situation is all a bit of a mess, isn't it?
If the endlers are in danger with the kribs (which they are, as you've sadly experienced), and you have angelfish (which again would put the endlers in danger, although they would have more places to hide in the bigger tank), then there only seems to be one logical conclusion as to what you should do, to ensure the welfare of the fish as it’s unlikely they’ll be happy in a tiny fry trap. Hopefully you have worked out for yourself what this logical conclusion is, but, if not, it is to keep the endlers in the small tank on their own (not in the fry trap where it's likely the stress of such a confined space will affect them negatively), and to put the kribs back in the main tank.
However, you mentioned the kribs fighting in their larger numbers but, in my opinion, this is likely to be better than certain death of the endlers in with the kribs or angelfish or stress being inside the tiny fry trap - Sue is probably best placed to advise which is the "best" of these difficult / bad situations, though, so maybe best to wait until she replies.
The "best" option all round is probably to buy a third tank (cheap, plastic ones can be bought in places like The Range), heater and filter, and move either the endlers or kribs from the small tank into that (after transferring mature media from the filter in the main tank into that new filter). However, you then run into the whole risky partial "fish-in" type of cycle situation again.
A responsible fishkeeper needs to be able to work out the sorts of issues above for themselves such as the most logical conclusion of where to place the fish in the circumstances but also a realistic one. If you haven't worked this out, then I don't think that you're ready to be able to take on more fish such as the panda cories you mention. I think you need to wait a few years when hopefully you'll be more mature and able to work these things out for yourself.
Hopefully you recognise that this is all a bit of a mess, and also that humans are not always that reliable (eg the people who were coming to take the kribs) and so you need to be able to plan for that possibility and have contingency plans in place.
How soon are the people likely to turn up who are getting the kribs from you? If they’re not reliable, then you might want to consider advertising on
www.aquarist-classifieds.co.uk – that will also increase the likelihood of them going to an experienced and, far more importantly than experience, a
responsible fishkeeper.
Hope that helps.