I never found a reference for that 10.000uF 35V capacitors at the manufacturer. Maybe they are only for OEM or they are fakes. But sincerly, i've takin apart some larger amplifiers for speakers and the largest capacity i found, was 8200uF. Also keep in mind that the elko capacity can rise when you use them below their volt-level after some time.
Is the Alps poti well grounded? Can you hear it with your headphones, if you touch the volume knob?
And sorry to ask for it again, but did you measure the dc-offset? :)