The snow line doesn't allow grains of ice or methane or other hydrogen compounds to form inside of its limits. Without massive grains, radiation pressure will kick out anything smaller than ~1 micron.
The water would still be contained by the solar system's gravitational field and would condense with itself and other cooler objects in both the interplanetary space
Yes, in the comets and the ice giants--not on the early Earth. The early Earth had its atmosphere stripped and was likely not differentiated prior to the impact event that formed the Moon (hence there was probably no geomagnetic field to protect it from the solar wind). There wouldn't have been any water on the Earth during its early years that wouldn't have been rapidly sent to the outer solar system.
The planet is mostly Ni and Fe
You mean Fe, O, Si, Mg, S, and then Ni. There is a lot of Ni, but there is a lot more of other stuff, especially iron oxides and silicates.
Most of the mass of the earth is in the core which is composed primarily of nickel and iron. The light stuff, oxygen, silicon, carbon, nitrogen, etc. is found mostly in the crust.