Wow sounds like a handful. A few things to think about.
When an animal acts defensively and then gets the wanted response from the predator it reinforces that behavior. For example you open your enclosure and attempt to reach in for whatever reason. Your snake thinks you're a predator so it hisses and strikes when you get close. You jump back and close the cage and leave it alone. In the snakes world that is about as good as that situation gets.
If the snake isn't eating, I would cover all sides of the cage to limit its stress. Especially if its striking when you walk by. Only bother it to clean and change water.
Work on getting it eating consistently.
If the snake is eating, I would still cover the enclosure just to reduce its general stress. but then I would start handling the snake. Eventually it will learn you are at most an unpleasant experience, but not a threat. I still have snakes that hiss and puff sometimes when I pick them up but put up with it.
Ending your handling sessions on a good note. Don't put them back if there not relaxed. If you pull it out and its striking, try putting him halfway on the floor. While still holding the back half, try to get him to start to slither away and keep moving your hands up underneath until it's just you holding him while he's moving. I usually don't handle for more than a few minutes at a time.
As mentioned above a smaller tub size might be a real help to make it feel more secure.
Good luck
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