Why dont you just sleep in Bandirma, there are many hotels realy close to the ferry.
Unfortunately the earliest bus leaves Çanakkale at 10.00 for this so you need to either book for a later ferry or arrive the day before and spend the night in Bandırma.
Canakale is very close to Bndirma, stay there for the night and have a nice breakfast in the morning, the hotels are well priced.... I have stayed there a couple of times coming from Ayvalik, although only driving my own car.Edited: 12 August 2016, 00:05
I see, thanks for advice. I have already paid for the hotel in Canakkale (before noticing this issue), so can't sleep in Bandirma. I would prefer the ferry but now I think Ill just opt for a long 6 hours bus ride directly to Istanbul. This way I will be in Instanbul around 2 pm. With a ferry on weekdays it would be only 6 pm. Shame they don't have 12:30 pm ferry on weekdays.Edited: 12 August 2016, 23:42