Where do i start
,
first point, if you are left eye prominent, by this comment i have to presume that you are a right handed player, i have taught Sergey about lining shots up using diferent eyes, so i would ask you to go back to him to look at your walk in, this is one of the rare points that i cannot teach by email, someone has to physically look at you, Sergey has the experience.
The next point, after practising 6 days a week for at least 10 years my record for the blacks off the spot is 443, i didn't miss i just got bored and stopped.
The next point, the snap shot, as it is called is used to illiminate faults in cueing, it is definately not used on all shots, Dave Harold is a personal friend of mine, he has taken this to the extreme, which because of the incredible speed of the professional cloths he can do this on all shots with limited success, as soon as the cloth is slightly slower Dave cannot play at the same standard, this has been his problem with consistancy for a number of years.
Wrist action has to be taught to individuals, again this cannot be taught by email.
What do i think of when i am playing a shot, this is very simple, only the object ball entering the centre of the pocket, everything else is pre thought away from the table, if you fill your mind with too many things then it is impossible to play snooker at high levels, each discipline you should learn so it becomes second nature and you automatically acheive this without thinking about it.
When i am training professionals i spend hours upon hours on the very small movements of the cue action breaking it down to the smallest detail, so under pressure it becomes very reliable, if you look at the way you practise i would suggest that you practise cueing exercises much more than you are doing, the simple fact that you are asking this question suggests to me that your cue action is not yet pure, the more you do these exercises the less you have to worry about cueing.
I hope that i have answered all your queries, best wishes Alan.