From the look of THE oil in your differential clearly you have a water contamination.
THE chunks of metal that you found are a sign of heavy or improper use .
Best world be to have a deeper look in to it .
What I would add is a repair kit for tires .
Not just string plugs , but mushroom plugs ,but also a tube , patches for side wall of the tire , cement , and a HD sewing kit for tires .
You can repair tires that have big sidewall cuts , 5-10 cm ...