The control buttons are only about 10x10 pixels in size, it's making the game barely playable. Is there a way to enlarge the user interface while still keeping my screen resolution?

dgVoodoo should solve that (this wrapper is really useful for this kind of thing on pre-DirectX9 games).

Get it here: http://www.dege.freeweb.hu/ , and follow the Quick Guide on the page (you'll need the D3D .dll files, and personally I prefer to set up game specific configs).

Then increase the Resolution in the DirectX tab. For example I'm playing the game in 4:3 so I use the maximum 4:3 for 1440p (1920x1440).

Now that will get you sharp graphics, as if the 3D engine managed this resolution natively. To get readable interface however, you need to keep the game resolution quite low, as this is what will define the UI scale from now on (1024x768 or 1152x864 are fine on 1440p for example).

However you need a specific setting to prevent the glossiness from disappearing even when turned on (the metallic shine on the menu ship for example): choose the videocard model 'GeForce4Ti 4800' instead of '3D accelerated card'. Maybe the other presets work too, but I've found this one is fine and stable. This may change with future versions.