Bethlehem is a suburb of Jerusalem. The Dead Sea is an hour away and you can either go by public transport or take a tour (e.g. the Abraham Hostel tours). Tel-Aviv is an hour away by bus. You can also take day tours up to the Galilee (e.g. Egged Tours) So if these are your only destinations then the apartment is a good idea.

However if you want to rent a car and drive around the Galilee then you should have another base in the Galilee. If you want more than one day in Tel-Aviv or are thinking of taking the train from Tel-Aviv to Akko and Haifa, then split your time between J'm and Tel-Aviv.