I dont know how being able to shoot at goal is not an obvious opportunity to score. Yes the obvious opportunity is interfered with but it isn't denied.A GSO is not enough. It must be an obvious GSO. And that was denied - the player is now trying to shoot while being held, which is not an obvious opportunity to score a goal; it's barely an obvious opportunity to play the ball, and only then because we know that they managed to do so.
Playing advantage would be the wrong decision, so this shouldn't apply anyway.
But let's suppose it was DOGSO-F and advantage is played because they managed to shoot.
The player can only be cautioned for USB if the DOGSO-F offence was an attempt to play the ball and a PK was awarded.
Since holding is not an attempt to play the ball, this cannot apply, and the sanction must be a dismissal.
Playing advantage wasn't wrong on the OP as he scored a goal so why wouldn't you wait and see?
To say playing advantage was wrong when a goal was scored is contradicting law and spirit of the game.
If he misses you then make your decision. If he is 1 on 1 with the keeper chances to score are not much more obvious than that.