what time should I travel from Hangzhou to Pudong airport, dep. time 1.20am? when is last train?

You can take high-speed train at Hangzhou East Railway Station and get off at Hongqiao Railway Station. The duration is about 1 to 1.5 hours. The schedules are from 07:30 to 22:25 with the frequency of 15 to 30 mins.
Then take airport shuttle bus line 1 to the airport directly. It takes around an hour. Notably, the operating hours of shuttle bus are from 06:00 to 23:00. If you cannot catch it, you need to take a taxi to the airport at a cost of around CNY280.

Or you may consider taking direct shuttle buses at Wulinmen CAAC Ticket Office, and arrive at Terminal 2 of Pudong Airport. The departure times are 05:30 to 17:00 with the interval of an hour. The whole trip is around 3 hours. In this way, you need to wait for a long time at PVG.