You're doing the right thing
What I normally do is print off the schematic as you have and use my probing in combination with continuity checking so I know what side of the component I'm probing e.g. C1 I'd continuity check which side is connected to in, probe it and mark with a tick on the schematic if it's ok then do the R5 side and so on marking as I go with ticks for ok and Xs for dodgy
I'll also often note the voltages on the schematic what they should be if I know and what they actually are
Basically giving you a visual of where your likely problems are
With this you do have more than one path going into the eq you can see where traces join with the dots letting you know its connected it's a baxandall set up boosting and cutting your bass and treble frequencies through Q3 I think obviously depending on the pot positions
So you will hear differences as you have at the transistor outputs depending on the pot rotation e.g. gain cranked more distortion bass CCW less low end etc
So once you find a problem ie something with little volume go back and try to pinpoint where it's lost and review your findings we know for example Q1 C voltage is more what you'd expect at 9v as
@Coda said and youve got 17.7v going into R2 so you'd expect double what you're getting there
Did you ever just lift the R2 leg that connects to Q1 C out to see what voltage you got on it
Debugging although it can be a PITA and you just want to get the %^&*$# thing going does teach you a lot if you're more of a layman like me and can actually be enjoyable when you get those eureka moments where you go sh*t that's loud oh that must be an amplification stage.....I've learnt something......who's a clever boy then!
Me, that's who gimme a $%@^&^× biscuit
