AZE, Your shot is a viable intentional scratch, although I don't like the chance of hitting the shot a little too long and running into the 4 ball when coming into the 5th rail.
Obviously this is a bad situation and your options are not good and very limited......But here's one other option that I might very well choose, if the table has super tight pockets, rolls off a little, or I'm playing someone who doesn't shoot super straight......I'll roll out an inch to the right, freezing the cueball onto the rail, on the point of the pocket......I'm purposely leaving him the straight in shot on the 4, but I'm leaving him just enough room to see/make it, and he has to shoot exactly straight/parallel to/along the rail......On tight pockets, or with the slightest roll-off of the table, this shot is not automatic and could easily be missed, and, unlike the other options, the potential payoff is killer - if he misses, he leaves you the 8, with either the ball you just spotted or the 4 ball as your next shot, giving you a great chance to run 3 and out and win the game.
- Ghost