You're basically just giving them the ball as the main result is it deflecting off you and going out for a throw. Would much rather have the throw in or the 50/50 chance the clearance falls to a teammate if it stays in.
Depends entirely on the situation but what if the defender sees you back off, controls the ball and they retain possession. I'd put the block in most times.
Well as a striker I always tried to show the defender inside, if he still tried to clear it out then I'd act like I was going for the block but pull out as soon as he starts to kick it. Definitely a situational thing, but it worked many times for me in my organized playing days.