Thanks for playing the game!
1. Yeah I have to agree, I've reworked the UI a bunch of times, and while I personally have no trouble following along, I can understand it being really hectic. There's a reason why I asked if I could borrow whoever made your UI once they're available. For the record you can hold 'C' to slow down time and see your cards completely.
2. There is rebinding, it's in the options menu. It's a bit wonky but it should work.
3. The scrap gun ('X' key) damage is tied to the scrap amount, i.e. the amount of gears. You get gears by dealing damage and certain cards give them, like the basic Cannon spells for example. This should've been explained in the tutorial, but if this isn't the first time you've played the game it might've not proposed the tutorial for you. I think for future DD I'll just reset player's local preferences so it shows the tutorial regardless.
4. Bottom left is cards in deck, bottom right is cards in graveyard, small bar is just the progress until you get another gear.
5. There are a couple of cards that you can use once to heal, but maybe I could make them appear more often, or have a rest site like Slay the Spire or what not. There are also daemons that give some, but not many.
6. For DD I hard coded it to 1/3 change per battle, precisely so that players can play around with them, but seems like you got unlucky. Regardless 7th (or 9th I forget) room is always a room that gives a daemon at the very least.
One again thanks for playing, looking forward to playing your game soon enough.