If the filter has some sort of media that removes ammonia/nitrItes or nitrAtes could give you flalse readings. Judging by your post, it sounds like you are doing great and about finished with your cycle. Once you get 0 readings on ammonia and nitrItes, do a PWC
to reduce your nitrAtes and you will be ready for your first critters. I hear some people don't really run their skimmers and others that do. You'll have to wait till one of them posts, since I don't run a skimmer.