There must be a reason they’re not allowed in the Mos Eisely cantina. Maybe Wuher is just a dick?
We had not one, but two droids working as bounty hunters in ESB. Their clients must consider them sentient, or else why pay a droid to do your dirty work?
As for feeling pain, Artoo screams when he’s hurt. And then there’s the infamous droid torture scene in ROTJ.