Thanks for the report, I'm just a single developer and don't work on this full-time so it often takes a while before I can return to the project. Thanks for your patience! To answer your questions and feature requests;
1. The pivot points are placed at the most logical position depending on the model. So walls will have pivot points at a center 1 x 1 meter square for easy rotation, and wheels in the center. It's to help users.
2. I've just tested all possible rotations and couldn't replicate your issue.
3. G to snap to a face is only available when placing a new block, but not once a block has been placed.
4. Objects should automatically adjust to the height of the block you're placing it on, no need to hold any key or button.
5. A hierarchy is unfortunately not available.
Hope that answers your questions!