The fuzz control is acting as a variable boost, my only concern is that it will mainly add boosting to the bass frequencies rather than treble, which may lead to muddiness rather than just fuzz.
The DpSt adds clipping diodes as well as a 50n cap parallel to a 5uF (Remember, caps divide in series and add in parallel), as far as I can remember, that should help with harshness of the treble. it won't add much more frequencies in compared to the 5uF it's paralleled with. Idk about that whole sawtooth comment, doesn't make much sense to me how that would work because of the cap. You'll need a pot with a switch to accomplish this the way the schematic & text refers to it, a stand alone switch may be neat as well.
I don't think it's that impressive personally. Just a fuzz with a pot and built in switch. The post fuzz part of the circuit is where it gets interesting for me. Q3 splits the signal and Q4 sends it to the output. Q3's emitter then goes to the trem part of the circuit. That's where I run out of help, I'm not that informed on phasers and trems and such.
S2 looks like a bright switch. The volume pot is just an attenuator/ voltage divider like any standard volume pot.