Just to visit Curacao and learn about the Jewish heritage there, how much time (days) do you recommend?
You can complete your efforts in a day or two. The Emanuel synagogue visit also has an interesting museum and bare bones gift shop. This is in the center of the capital. There is a small Jewish neighborhood with gentrified homes. There are also 2 Jewish cemeteries. Enjoy your stay on this scenic island!
An hour or so should be more than enough unless you stay for a service.
I would suggest at least two full days (not Saturday).
Get quick answers from Mikve Israel-Emanuel Synagogue staff and past visitors.