Sorry to hear aot your experiences.
As others have said chain breakage is rare, but your story shows it does occur.
No doubt corrosion
was the biggest factor, but 8mm, probably G30 chain is a little light for your sized boat.
New gypsies are expensive and as you noted chain is heavy.
Have you considered hi tensile G70 chain?. I think 8mm G70 would be OK for your size yacht. It has a similar strength to regular 10mm chain.
Italian Maggi chain is some of the best and can delivered to Greece
probably for a similar, or not much more, cost to local 10mm chain. You would not have to change your gypsy (with considerable saving) and there would be no weight penalty.
Finally Greek waters are so clear that your anchor should be easily found and retrieved with just free diving
I am sailing the area (although it is a big country with a lot of scattered islands) if you want to PM the location where the anchor was lost
I may know someone near the area that could pick up the anchor for you.
I expect you don't want the chain back