Before I select a method for saving my my large 2d rpgs map maps full of custom objects (Fighters, Books Potions, Wands, Armor, Buffs, Weapons, Scroll, NPCs, Buildings ECT.) that is too slow or won't meet my needs.

I want to know what would be the best way or least a good way. I want to have maps of at least 500*500 32*32 tiles. I'm using the TiledMap libGDX class for the map but the objects are all my own using many abstract classes and the KPCOFGS(Kingdom Class Phylum Order Family Genus Species) method.

I have gone with data driven editing as opposed to scripting so my classes have many editable fields to change various things about them. The fighter class has over 100 fields for things like various kinds of armor, the weapon , the packs, strength, strength increase, experience, Iq and many more). I have an editor written for these. They then get placed on the map and in lists stored in game objects class that Game Map has access to.

My question is what would be the best way to save the map and all associated objects to load at a later date? I would like to able to save the maps on windows, mac and linux and load them on windows, mac, linux, and android.