Steam wand leaking, no water from brew head, odd brew button behavior

I picked up a secondhand machine that I'm trying to get working again, but I'm having some issues. Initially, the steam wand worked fine but nothing came out of the brew head so I did a full disassembly and cleaned everything, including soaking parts in citric acid to remove calcium buildup (there was a lot). When I reassembled everything and ran the machine, I noticed the steam wand began leaking as the machine heated up, until the ready light came on then it stopped. When I pressed the coffee button, however, water came out of the steam wand instead of the brew head, as if I had activated the steam wand despite the knob being in the off position. I ran a cycle of Dezcal, thinking there might still be some buildup preventing water from flowing to the brew head, but nothing changed.

After reading some answers to other questions here, it seems like my problem is that the steam wand leaking is preventing enough pressure to activate the mechanism that allows water to flow through the brew head. I've taken out the little hex screw and tightened the knob as much as possible but that didn't fix the issue either. Is there something else that might be causing the steam wand to leak? I'm also concerned about the coffee button behavior; is that just a result of the steam wand issue or is something else wrong?