Spawning too many Objects when loading the World (k_eresultlimitexceeded)

I am trying to add a Multiplayer to my game, but the way I currently try to load the World on the Client does not work and only loads around half of the world.

Currently when loading the world on the server I use NetworkServer.Spawn() on every important Object (these being Chunks, Items, harvestables and animals), I do this because this is the only way I know how to spawn the Objects on the Client without respawning the world everytime someone joins. This has the added negative of not being able to control how much information is send at once, thus when a Client joins they get too much information and after a short while of loading the server gets first a warning then an error ("k_EresultLimitExceeded") and the world is only half loaded on the Client, I don't know any way to slow the transfer of data down or to load one chunk at a time without doing so on every client at once.

So my question is, is there any way of either Spawning something on one Client at a time (being able to request a spawn as Client), slow down the transfer when joining or just raise the limit of how much you are able to send.