Normally - IF - you know you have plenty of film build, that is plenty of topcoat paint to sand and buff - then you sand until the paint is totally flat. When I look at your pictures, I see a lot of shiny spots - which are the low points that have not been sanded.
Ideally - you sand until the entire section of paint is dull with sanding marks.
If you're unsure - to me - it looks like you need to continue sanding, but let common sense rule the day. Any amount of sanding is going to reduce the level of orange peel and thus the paint is going to look much better.
If it were me? If you know you have plenty of clearcoat to sand - then I would continue sanding with the 1500 grit until the paint looks completely flat. Then move onto the next grit level and refine the 1500 grit sanding mark to make them more shallow for faster/easier buffing.
Great start!
Mike