The stop is dead. It is covered. He can throw it, but 90% here would bitch he threw a 5 yard route on 3rd and 8 even if you think the ball could get there before the DB, which is highly arguable. You 100% correct in the fact this is a really poor play design, which is a way bigger issue. There needs to be someone on some type of crossing route running to space to give the offense a chance to get a first down. Preferably, there would be a half field read with at least 2 short/intermediate routes. Having 2 short routes on opposite sides does not help. I really dont understand the idea of 3 verts with stops attached in that situation given the pass blocking issues. I am not sure all that matters, because the DL has beaten Stroh before Arch's gets his back foot down. Arch is going to have to throw immediately at the top of his drop and still going to take shot. This play was dead the moment it was called.