Nausea and dizzyness are fairly typical of ketosis. I have to limit coffee too or else I really get a buzz. I have green tea or some decaf in the afternoon.
You might want to add a little potassium by using some salt substitute.
I don't get much nausea anymore. I guess our body adapts. I did a 21-hr fast yesterday and felt great. I am going to fast more frequently, probably M-W-F for a while. I'm not even going to mention my body fat %!