I would just take the bus at 3:50. If you land at 2:30, you won't be off the plane until 2:45, train to immigration and be there at 3. Get your bags, 3:15. Pee, buy the bus ticket, get a bottle of water or something, 3:30. Then just wait in line for the bus (At that time, it might even already be there).
Unfortunately, with airport taxis at that hour, you could be overcharged or it could just be messy. They might not want to use meter, and they'll just flat rate you and refuse meter.