I'm facing almost same problem, but a bit different, I'm also using the same code, but I'd like to:

1. Light two decimal points at same time, while maintaining decode mode on?
2. Enable free mode, when I can light up arbitrary segments, but only for part of display? say I have 4 digit 7 segment display, I want two leftmost chars to display "AC" and remaining two chars to work in decode mode?