Floating bricks don't exactly work in Blockland as you would expect them to.
If you want to use hacks to make the brick float, or in other words do what you are trying to, then you will not be able to hammer any bricks attached to it because the game thinks that brick is supporting all the bricks it is attached to(because there's no ground), and for that wanding bricks will destroy all the bricks attached to the floating chunk you're trying to destroy.
On the other hand, you can also use the Zone Bricks mod. Zone bricks have cubes, and when you place them they are automatically transparent and uncolliding, and you can plant bricks anywhere inside the zone cube and that brick will be supported by that cube. The problem with that is if you're trying to destroy a large area of bricks inside a cube, you either have to destroy the whole cube and each and every brick inside it with it, or each brick one-by-one.