Welcome to ToS and the crappiest mouse interface I’ve ever seen in a game!
There’s no way to remove that. Best you can do is move it in a corner and forget about it. But since the game doesn’t record UI positions, you have to do this every time you play. Note that this is not the worse movable object, there is also the huge “party info” slob to the left that you will inadvertently click a zillion times while you play in party and drag it instead of seeing your character move.
If you talk about the HP/SP/STA bar to the top left, yes you can (but there is no reason to). If you talk about the bar under your character, no you can’t, you can just hide it if you want with one option on the right.
None that I know of. Otherwise I’d use them immediately! You can’t imagine the hell it is to play this game when both moving and targeting are set to the same mouse button and always clash while the other mouse button is used for nothing. Wait until you do Vasilisa raid using mouse while her hitbox is bugged, making you unable to move and AA locking each time you click somewhere…