Hi,
first things first:
* use the protection on the RS485 lines.
* improve the PCB layout.
If heating is the problem, then no capacitor can avoid this
Also on this non optimal PCB layout (not following the datasheet guidelines) no capacitor can work "as a capacitor" because of the high series impedance of the PCB traces. So changing capacitors will have the most impact on a optimized PCB layout.
Mind: not the trace thickness, nor the trace width have big impact on the stray impedance, it´s the trace length and the combination with the return path (vias, GND_plane).
There are many, many threads here in this forum about circuit problems caused by PCB layout.
****
LM2576 is a switching power supply.
Klaus