3hrs    Sorry I have a hard time believing that...

45-60 hrs if you're a noob. This isn't a fender champ kit!

Between 20-30 hrs if he has done this type of amp before.

Small amount of fuzz; due to the 12ax7 on v1 you got more signal going through the wires so it possibly is less prone to heater wires magnetics. Still a suspect of the fuzz that's left.
v1; clean
v2; od
v3; phase inverter

Achim:
Tubes: put a 12ax7 in v1.
The 12ay7 has a estimated 40X amplification. A 12ax7(ecc83)  has 100x.  The voltages at plates of a 12ay7 might be completely different and can have the opposite effect by clipping earlier due to shifting plate voltages. Best is to use the tubes it was designed for.
Sorry, it is too long tech talk to go any further into this subject here.

For heater wires etc. I recommend you go to a local tech.

Having a fuzzy sound on the overdrive can have multiple causes.
Most often it is caused by signal wires that are too close to the heater wires.

Your complain on the lack of headroom maybe a tube thing.
In your case, check your tube voltages, swap some pre-amp tubes or when not comfortable with these options I would take it to a tech with some OTS knowledge.
It is shooting in the dark giving you advice without getting actually in the amp.
Speakers you have are one my favourites with OTS amp.

I one of my cabs I have Celestion G12-65. Recently I tried someone else's cab with WGS ET65. The ET65 is not as creamy as the g12-65 but the ET65 has way more highs. It's a very nice sounding speaker.

Your wiring is the possible problem of the oscillations, they are on various points crossing other wires or sitting on them where they shouldn't. Not just 1 wire; all over.

The voltages; I couldn't see the colours of your dropping string correct; maybe post a better pic of that. However the last dropping string resistor; you have a 22k instead of a 2k2!

Yeah you're right my bad.. To the OP; Check your wiring for the od trim pot on the back.  measure in Ohms. Sometimes when heated too much, the insulation of the shielded wire is touching the leads.
It is also good to go through the whole schematic and measure each connection. Work yourself from relay Od input to PI input.

Check your cathode resistors at the phase inverter. Those voltages at the v3  grids and cathode are too high.

Maybe you can post a pic with the marked item. It's very hard to tell what exactly you're reffering to.
Edit: you mean the relays?

If your leaddress is not OK the EVM12L can be revealing; very harsh tones.
If your lead dress is ok it should sound good. Lots of highs and in your face sound is how some people describe it.

Just unsolder the secondaries that go to ground and rectifier board, also the bias tap and filaments. 'Don't mess with the PT paper covers, just look where the wires go and unsolder them. You could use one of Nik's splendid layout for orientation.
If this too difficult: consult a local tech.

With  no power: disconnect all secondaries and measure the 345-0 and the 0-345 taps in Ohms.
Both sides should be the same; if you got around 20 Ohm difference the PT is gone.
They should measure around 40-50 Ohms per side. When measuring both 345 taps it should be around 90-100 Ohm.

Don't do it, it's forbidden in most countries.
If those caps fail, you have wall AC on your chassis and your guitar.
Although it may do wonders for your haircut