The machine reader will read barcodes on self-print BPs. Having said that, this is based on my experience with other airlines (SK, LX, SN) not 9W. There is usually no one to help you with this. You may just want to check at the counter, if time allows.

Sunday mornings are better than weekday mornings with regard to the security queues; ime the fast track will save you a few minutes at most - unless there happens to be a bunch of charters departing at 11:00. Most 9W pax transit through the mini-hub in Brussels. If you ask nicely, you'd probably be able to move to the front of the queue if fast-track doesn't work and your flight is already boarding.

Although trains are generally reliable in Belgium, please do bear in mind that this is a relatively tight schedule, especially if it involves train connections. You might be better off arriving back in Brussels the night before and save yourself lots of potential stress.