How many ways are there to lava-proof blocks?
I know that chests-with-items' supporting blocks can't be broken, so a Chest With Something on a Table on a non-lavaproof platform likely means that all three of the blocks can't be destroyed...
Presumably this applies to https://terraria.wiki.gg/wiki/Mannequin on PC as well:
Mannequins can only be removed if no items are placed on them.
Are there any other methods?
Lava does not destroy most tiles in Terraria, so you don’t have anything to worry about. There is no fire, so even wood can hold a pool of lava.
The exceptions to this are platforms, so I would recommend the use of Planter Boxes in their place, which can be purchased from the Dryad. These have the same properties as platforms, but allow lava to pass through without destroying them.