Water everywhere

Lately I've been reading about water. How did all our water get to earth. There is a lot of it here. It makes up 0.4% of the earth by volume, about 326 000 000 000 000 000 000 gallons. That's a lot of water. For most evolutionary theories to work, water had to be present in large quantities early on in the earth's development. The problem is that the early earth was hot and dry, molten lava cooling slowly. Also, the early earth had no atmosphere and the solar winds were strong so any formation of water vapour would have been whisked away into space. Hydrogen and oxygen should have been present so the capability to make water was there. The problem that I see is that water needed to have formed fairly quickly in the geological clock, in around 150 million years according to most theories. If it took significantly longer, there would not have been time for the long, slow evolutionary process to occur. To get 326 000 000 000 000 000 000 gallons of water the earth would have had to receive 16 500 tons of water every minute for 150 million years. And that is not considering the water we lose to space by the disassociation of oxygen and hydrogen that is taking place on a tiny but constant basis. There are two main theories on how our water got here. It may have been formed from volitiles in the earth's crust being expelled by volcanoes outgassing or the water may have been imported here by falling comets. Neither of these seem reasonable to me. I can understand the physics of this happening but I can't imagine how either of these could have supplied anywhere close to the amount of water that we are talking about. The articles I have read don't supply any reassurance. There doesn't seem to be a logical physical explanation for it.