Im still trying to get a handle on the 30ml in 30 seconds bit. I think I dialled in a good extraction but it comes out as more like 60ml in 30 seconds.
If you are using a double basket, then you should expect ~60ml in 30sec. A single basket would give you the 30ml in 30sec.
Do you own a shot glass measuring cup? If so, with the double spout portafilter, pour espresso into your usual coffee cup under one spout and the measuring glass under the other. You should then see the 30ml in 30sec in the measuring glass. A naked portafilter should not change the volume or timing of the shot.
Also, if you are using older beans from last year for practice, chances they are well and truly stale by now and old stale beans will not pour the same as good fresh beans. Stale beans will not have the oils needed to provide the extraction resistance and will always pour much quicker than fresh ones at the same grind setting, therefore needing a much finer grind to get the right timing/volume.
The general consensus around here Ive noticed is that it is a bit of a false economy practicing on old/poor quality beans, as youll never get a great coffee from them, and good fresh coffee beans will always require a change in your technique when you get them anyway, so might as well use fresh beans from the start.
As far as your Question 1, I think a puck stuck to the shower screen can indicate underdosing? Happy to be corrected if wrong.
Q 2., not exactly sure, ? also an underdosing issue.
Hope this is of some help.
Good to hear you are enjoying your set up, sounds like you should be producing some great shots in no time once youve got the hang of it.