Force combat button disappeared when I hit uranium or titanium (can't remember which), wish it was back, it made the game more fun even though it didn't help much.
If anyone wants to know, the treasure inside chests goes like this: red/gold = artifact (100% chance that I've seen), green/gold = potion/wings, silver/brown = normal equip, brown = crafting material
The initial advice you get is not so great later on, some monsters that you've been fighting for a few floors become so weak they inflict no damage, essentially giving you free exp. Make a point to kill as many of these as you can.
You can click on the upgrade bar to set the upgrade level.