Im not 100% sure for gl'bgolyb always being fuchsia bloods lusus, but wasnt it like a thing that doc scratch put it on the planet for the condesce to take care of that was passed down to feferi to take care of? So in a roundabout way to answer your question, probably?

For your second question, eridan helped out feferi because he had a connection with feferi, I dont think its strictly needed for ALL violet blood to help feed lusus to gl'bgolyb, so no, I imagine anyone can just help feed it as long as it got a steady stream of food.