If I drop the course now, will I be considered as GAP year student
Unfortunately not. It's past the semester's census date so you will have a tertiary academic record of 3 subjects (even if with no results). With this record you are ineligible except for the 5 schools we have mentioned.
This being the case, if you are not planning to do something else in semester 2 I'd suggest you take on 2 subjects. It would make no difference to your application status to these 5 schools, but if you are not able to make into med you will have 5 subjects under your belt instead of 3. (Don't do 3 more though as that would take you to 0.75 FTE and the GPA will drag down your ATAR Rank for UNSW).