If a QB is being hit as he throws, he can't go thru the process of "electing" what to do with the ball.
Also, there are plenty of schemes that disguise coverage so a receiver seems open when he is in fact not. Certainly the credit should go to the defense on a play like that.
I can think of no better example of "decision making" than
being able to accurately read a defense, so I'd say tricky defenses still fall under the umbrella of unforced errors.
If you're going to file "well, I didn't know a defender would be there!" under
forced error, you've just defined unforced errors out of existence. No QB thinks a defender will be where he is throwing the ball at the time the pass is thrown.
If you're talking about passes that are altered because the QB was hit before the throw was completed, sure, I guess you can file those with strip-sack-fumbles and tipped balls? I think that's a small minority of INTs.
If you don't have an open receiver to throw to and the defense is going to sack you unless you throw the ball, then the QB is in fact forced to throw a bad pass because there is no good pass to throw.
Again, you have the option to throw the ball away or take a sack, both of which are preferable to INTs.