i looked into that a while ago and the alu molds seem to be the best bet - for the recycling:
i am not sure in how far you can re melt them - plastic changes the molecular structure on hardening and the bonds it forms can be rarely be broken apart again - i worked summer jobs in a plastic injection mold co and the rest of the batch needed to be shipped of again and could not be grinded up and be reused - but not sure how that works here with a different type of plastics much more soft
but hey - give it a try and let me know - but when i do the huste of injection mold - nothing else makes sense in my eyes for the bait
i think i'd rather mix a new batch instead of wasting my time wit used plastic