have you tried increasing your client ram usage?
-Xmx2G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
Pixelmon dev said that i should increase the ram on the client itself to get the lag gone
about the errors being spammed that dosnt happen for me and i have the latest release off Pixelmon + MCryfish Furniture mod, Custom NPC’s + WolrdEdit
so its a different mod wich is causing the problem
if the problem still is being caused then i would suggest you contact @MoeBoy76