I don't think 30 seconds is too long, but taste should be your guide. As long as you aren't blonding, or are just starting to blond by 30 seconds, I think it should still taste great. Personally I haven't noticed any deterioration or overextraction at a 30 second pull.
I read something on HB that an expert barista who teaches for the SCAA (Heather, I think her name is), uses only a very light tamp, and lets the machine do the rest. This, of course, requires the grind to be very fine, in order to create the required back pressure. I'll see if I can find the thread for you and drop a link in here. The method was super-simple -- nothing fancy or time-consuming.
If I used your method on my machine, I would probably have too much coffee in the PF, and then the shower screen would compress it and the shot would choke the machine. I have to dose so that the tamp leaves the top level of the grounds quite deep into the basket. I have to fill the PF very loosely (no tapping yet), level it, then tap on the counter to settle, and then tamp and polish. I guess your screen sits higher so you can fill your basket higher.