Pat, you owe it to these other little guys to report it, I'm sure you already know it in your heart.
As for Harley, I think he will be ok now, if he is able to gobble-up his food as you describe then he will be able to satisfy his hunger on his own, just ensure the food you are giving him is good quality food (which I'm sure it is anyway) and of a wide variety and yes I think suppliments would be a good idea until he builds his strength up.
God bless this little guy, he is adorable and he obviously sees you as his saviour - which you are Pat. Karma to you.