Q1 - My thoughts only. I've seen a luthier giving a workshop on re-srtinging a guitar. He was very particular about winding the minimum amount of wire onto the tuning shaft in order to maximise the angle between the shaft and the nut. Conversely (my guess) if the angle was (say) 80 degrees there would be better pressure at the nut, but the friction would make tuning difficult and the permanent bend would weaken the strings - hence the various convoluted knots that fisherpersons tie in their lines to avoid stress.

Q2 - I'll leave that to someone more knowledgable, but somewhere here lies a continuum between strength, density and the ability of the soundbard to vibrate sympathetically with enough volume and uniformity across the musical spectrum. Concrete is fantastic for speaker boxes if you don't want to move them and because the concrete does NOT vibrate sympathetically and hence colour the sound.

As an aside I knew a guy who bought a whole town's stock of street trees because the town was being re-located due to a mining project. He intended to use the timber for violin making. The trees in Australia grew much more prodigiously than their European equivalents and the timber was commensurately lighter (less dense)- and relatively useless for fiddle making. Fortunately he had an open fire - not typical of Australian houses these days.

Regards, John

Q3. - Addictions are just fine if you can effectively manage the outcomes. Is it an expensive addiction?

Regards, John