Some people tend to not want to believe the truth....and ignore it!
You have a thin-walled model that has a large amount of very shallow angled surfaces...and you are trying to print it with an extrusion that is sausage-sized!. Well, I exaggerate somewhat, but printing this sort of model with a 0.4 mm nozzle and a layer thickness of 0.2 mm, you are bound to get the solid infill showing on the outside surface.
You report that "the perimeter is showing gaps". This is not gaps in the extrusion of the perimeter....but the infill on pervious layers being visible on surfaces that are very close to level.
As I posted above, you need to at least lower your layer thickness down to as thin as the printer can print to reduce the number and depth of the "steps" in the sloping surfaces. Changing to a smaller nozzle size will also help improve the finish of the part.
And finally, with this type of 3D printing, you are not going to get a 100% smooth finish on surfaces that are a degree or so off flat. Some print in appropriate materiala that allow them to either heat the surface with a blowtorch, or spray the surface with solvent to melt out the steps.
See this thread for info on a feature request that would help your particular print: viewtopic.php?f=23&t=5814