The last bus from Pudong Airport to Zhangjiagang is at 17:40 and the first bus is at 12:50 in the afternoon. So, it is impossible for you to get a direct bus from Pudong Airport to Zhangjiagang directly after landing at around 23:00 at midnight. Unless you take a taxi. There are also buses to Zhangjiagang at Shanghai South Bus Station, the first one is at 06:20 in the morning and the last one is at 20:40 in the evening. Takes 2.5 hours to Zhangjiagang.
2. There are direct buses at Changzhou Bus Station, takes around 1.5 hours.
3. From Changzhou to Nanjing, taking bus is more convenient, takes around 1.5 hours.
4. There are more trains than buses from Nanjing to Yiwu, takes around 10 hours. Buses can be taken at Nanjing East Bus Station.