The best way to separate them is to cut off the fronds and try and save as many roots as possible. Let them dry out for a day (don't put it in too much sun though as it is drying out) so the cuts can heal and after that, plant it in good soil. This time of the year it will start to end it's growth for the season and I definitely don't recommend separating them with winter so close so if you can wait out until spring, that would be good. It looks like you won't be able to separate the pups without getting rid of a lot of the roots. It will recover fine with the roots cut off if the fronds cut off, but it will need some nice weather to get it going again.

Good luck!
-Alex