I have just found a baby song thrush, not sure of its age, but it has a good amount of feathers. I have been feeding it Pronutro and live earthworms, any suggestions on what else it needs to eat and how regularly?

Unless you're certified in wildlife rehabilitation, which based on this question I assume you are not, it is actually illegal to possess wildlife regardless of your intent. I would suggest calling the nearest wildlife rehabilitation expert and leaving the care of the thrush to them.  Unless you are certified and have studied these types of situations you could actually be doing more harm than good by caring for it.