Deep sea pumps that work on wind power, can they control the weather?
In theory your idea is not bad,But it needs to be placed as far from land as possible this is to avoid the soil on land from being contaminated by saltwater.

So spraying saltwater into the air is not usefull for creating rain over land,But it can be used to cool the ocean and the planet.

Salt water spraying into the air can possibly help creating condensation nucleus,And help clouds to form and these clouds can shade the ocean and limit the heat absorption.

But this is not as simple as it sounds,Clouds tend to form more in the evening and night when the temparature drops and not as easy in the daytime when they are needed.

Clouds can limit the heating in the daytime,But they will trap or reflect heat in the night time,And then the positive effect is limited.

I think it is best to use the hotter water from the surface of the ocean as it will evaporate faster and probably create clouds faster.