For number 1 you can just buy a quick chest and put some gear into and hide it. Or your team mate can distact them while you get the chest. Number 2, some island are going to be small, like solo maps, so your gonna want as much space. Cubecraft also made it so you cant place a block in 3X3 grid near the shop or generator. In the tiny image I made, it explains what I means with the shop/generator in the middle, and the blue squares representing where you can place blocks.
For number 3, yes I understand this is annoying but these blocks are always something cheap like concrete. So just take your pickaxe and mine it, its not going to be that tough to mine because they usually only place two blocks.