Yikes! You've got a challenge ahead of you, but I don't need to tell you that. I'll suggest what I would do if this were my plant.

First, I would cut the fern all the way down to the soil level, or nearly so. Then, I'd gently pries it out of the container so that I could scrub the pot and give the root system a little examination. Back in the pot (with little disturbance at this time of year), I'd examine what little sticks are left for any sign of mealies.

As your fern regrows over the winter, you'll need to be very vigilant about inspecting it frequently. Since ferns can be spot treated with alcohol, be prepared to do battle. You can also use insecticidal soap on ferns as long as you follow the directions.

By the way, it doesn't sound like you 'won the battle' with the cacti. ;-) I'd not let them anywhere near the fern. By the way, I've used an alcohol mist quite successfully on cacti that I have grown. You might try it on your cacti, in case you're missing the small eggs and crawlers.

I'll not suggest the alcohol mist for your ferns, but only because I haven't used it on that plant. Perhaps someone else has experience with that.