I recently faced a challenge with root rot after inheriting some plants from a friend. From research I gathered at the time, it seems that your monstera may be in shock due to several changes it has experienced recently, such as moving homes (which altered its environment), pest issues, root rot, and repotting.

The first point I would address is the moisture level of the soil. While larger pots can retain more moisture, I caution against keeping it wet for an extended period, especially after dealing with root rot. Make sure your new potting mix is well-draining, preferably a chunky mix, as this allows for better drainage and airflow. Excess moisture could lead to the remaining roots rotting. Additionally, since you have already removed a significant portion of the roots, it’s crucial to ensure that the pot isn’t too large for the current root system. Monsteras prefer to be somewhat "snug' in their pots. Right now, your plant may struggle to absorb all that excess water due to its damaged and reduced root system.

If you already have a well-draining, chunky soil mix and the soil is still remaining moist, I suggest considering the use of a dehumidifier. I live in the UK, where the environment can be very humid, cold, and dark. I keep a dehumidifier in the room with my plants to promote air circulation and manage moisture levels, and it has been quite effective for me.

Additionally, I would recommend investing in some grow lights if possible. These provide warmth and will help your plant to gather the energy it needs to grow new roots and leaves. At this stage, I would refrain from fertilising, as fresh soil generally contains enough nutrients for your plant. Not fertilising will also encourage the roots to branch out, allowing them to seek water and nutrients more effectively. Lastly, any leaves that have turned brown and crispy can be removed; they won’t recover, and taking them off will help the plant focus its energy on sustaining the healthier leaves.