For A: I don't know what you mean by "need to exit back to the menu for purchased upgrades to take effect." Upgrades update the frame after you purchase them except the big damage button which scales with the difficulty level. The icon in the bottom corner (which I am assuming is what button you may be pressing think its a back button) is just meant to save your game.
For B: I added in a button that will reduce the difficulty level so that you can see the monster on that level.