No sound doesn’t necessarily mean a power supply problem, no, but as you tested your supply and had no voltage you’ve answered one question yourself this unit does require power for bypass.

AC doesn’t have a polarity, but DC does, but hopefully the rectifier diodes will have provided some polarity protection.

There’s not really a thing as ‘too many buffers’ your signal doesn’t get over buffered.

True bypass is useful with specific pedals like vintage fuzzes that rely on direct guitar/pedal interaction but I can’t see anything in your chain that would meet that criteria and you already have a buffer first in chain (TU2) so the point is moot.

So if you like the pedal, go for it.

There’s plenty of articles on the topic if you’d like to learn more, here’s the first that came up http://www.roland.co.uk/blog/the-truth-about-true-bypass-and-buffered-guitar-pedals/

The specific version & if there’s any factory or prior user mods.

So it is (not sure why mine has a later date, looks identical apart from post dated annotations) still, the very end of ’77… I can’t imagine they rushed them out before new years eve

They did use old pots as you know which does seem the much more likely answer.

As for the #3, some of them had stuff scribbled on the boards, no idea what it means but that’s not the only unit I’ve seen with numbering.

Sometimes IC’s had dating, post a photo of the component side too.

The factory schematic for the Deluxe Electric Mistress is dated November ’78 so it seems quite unlikely there were earlier units, especially that much earlier.

No, the greenies and circular (and that red square one) are mylar and ceramic non polarized capacitors, they very rarely go bad and should be left alone.

Just those 2 blue and 2 brown in the centre as you say and the electrolytic are the barrel shaped capacitors.

You MUST make note of the polarity of these capacitors when replacing them (I usually take a couple of photos and then use a sharpie to mark the board before removing them) the stripe on the barrels indicates the negative and on the tantalums they should have a + symbol.

Also you need to make sure the voltage rating on the new capacitors is equal to or greater than the original you’re replacing.

Where are you located? In the US try The EH Man, in the EU, I can take a peek.

Voltage readings are needed to give any kind of educated answer, plus testing the slide switch for continuity.

But it will likely be one of 4 things, the switch itself, a bad solder joint, the 4u7 cap connected to pin 3 of the 1458 or the 1458 its self.