There are so many differebnt types of self-watering systems that it is hard to know if yours is a good one. Many of these pots keep the soil constantly moist and that is not good for your marginata. If the self-watering pot doesn't allow the top quarter of the rootball to dry out every 7 to 14 days, then the roots will rot.
Perhaps a wire sceen over the soil will keep your cat away and also allw the soil to breathe.
Boston ferns need to be in a window that gets lots of indirect sunlight all day long with little or no direct sunlight. A north-facing window would be best if it is not shaded by a
tree or building. This is most important.
The
plant should be in a pot that drains excess water away from the roots and out of the pot. Boston ferns have extensive root systems when healthy and will thrive when potbound. They tend to use a lot of water and do not like to get dried out. If they are in the right sized pot with good drainage they can be drenched without fear of overwatering.
When healthy, they can be fetilized with a high nitrogen fertilizer that is diluted by doubling the amount of water recommended on the label.
Low humidity is not a problem as long as the roots stay moist.
If you move it outside avoid temperatures below 55 degrees, keep it heavily shaded from sunlight and protect it from strong winds.
It is quite normal for underneath fronds to turn brown and dry as new growth is added on top. You can cut the dead fronds off. However, Boston ferns are fragile and don't like their fronds to be handled much. So be gentle with it.
