2) if the tamper is hitting the slope of the single basket, there's not enough coffee. A sloppy top of the puck is also indicating that.
3) try weighing the beans instead of worrying about the timer. 14g of beans is about right for the single breville basket with most freshly roasted espresso beans. You want the end result to be the post-tamped coffee just covering the top of the slope, ie. minutely above that level.
4) tamp to around 30lbs (use normal scales to about 13kg's if you want to get a feel for it).
5) you can use the razor if you want but imho it shaves off too much for the single basket. Minutely above the top of the slope seems best.
Once all the above is constant, it's just a matter of getting the grind setting right. For freshly roasted espresso beans it can be anywhere from 17 to 11 on the Smart Grinder Pro for a single basket shot. Compare with most supermarket beans where the setting is often more like 5 (and even then the result is poor). You're looking for a dark consistent creamy flow, around 25-28ml in 30 secs.