The branches of my fiddle leaf tree are dry and brittle
I can see from your photos the plant is locate in close proximity to a heating vent. This could be drying out the leaves and reducing humidity around the plant. I can also see the plant is in a small pot restricting its root system.
Repot the plant into a larger container and locate it away from hot and cold drafts. Increase humidity by using a humidifier or mist the plant regularly with plain water.