Bigguy2017

Yes, A to D spacing is very wide - looks like the string positions on the saddles

My ballpark setup is a 10p piece on the 12th fret just drags on the string (2mm). The Stingray is a bit lower - 1.75mm.

The Quiklok BS317 Amp Stand is solid, inexpensive and works for me... £39.00 + P+P https://www.andertons.co.uk/guitar-dept/electric-guitar-accessories/electric-guitar-hangers-stands/quiklok-bs317-amp-stand

Try Matty Dread on eBay - he's in Ireland and made me some replacement string pullers for a Hohner headless bass Steinberger tailpiece. https://www.ebay.co.uk/usr/mattydread2012 drop him an email...

Yes, if you spray some Deoxit D5 on some black plastic, like a CD case, and let it evaporate it leaves a lube residue.

Check the wiring of the cable - if it's an XLR is ground on pin 1?

Got a batter one?

Wow, that's a bit flash... A bit like the Tzar's toilet - in a nice way.... 😉

Obviously belonged to Jacques Cousteau...

Similar experiences in my teens. Jack cables were jack cables (and generally crap). But then again no-one was using more than 100W - usually less. Big transistor PA amps were what first raised concerns - MM Electronics rack units were 400W (?) and used XLRs - that's when we started making 'speaker' cables with mains twin core. The jacks themselves were always border line, XLRs not much better, current wise, and then Neutrik introduced Speakons.

Some in-out with a Krackle Killer and Deoxit D5 works wonders. Bending the contact is a bodge - better to order a new Switchcraft jack... which will last decades... The worst are the tubular jacks which need replacing every few (?) years. Avoid cheapo 'gold plated' connectors - whatever they are plated with (it aint gold) quickly wears off and gums up the jack contacts.

Best would be try for spares from the manufacturer. As other NZ poster suggested, try your local model shop for someone with a small lathe who can turn you up some new ones. A harder type of brass or bronze would be better. A cheap fix would be to clean and degrease the holes, fill with metal loaded epoxy (Epoxy Steel etc. from eBay) then cut and file screwdriver slots.

First try re-seating the valves.

Can you reverse the magnets? If so you could do a RWRP humbucking thing. EA in parallel, DG in parallel, then EA in series with DG like a P bass...

Nah, it needs a tone control.