The numbers issue is one i don't know how to fix without big changes. For fullscreen, you can edit the prboom configuration file manually:

• Install leafpad using app manager
• From xterminal:
  leafpad .prboom/prboom.cfg
• Under "Video Settings" section:
  • Enable fullscreen by changing 0 in "use_fullscreen 0" to "1"
  • Change "screen_height from 400 to 480
• Save the file

Alternatively, you can start prboom in fullscreen from xterm:
/opt/prboom/prboom -fullscreen -width 800 -height 480