I can't answer your tuner questions, but regarding rounded solder joints in high-voltage areas, spiky joints could encourage corona discharge (
https://en.wikipedia.org/wiki/Corona_discharge), which may lead in turn to high-voltage arcing & sparks (never a good thing).
That CRT cradle is ingenious! More secure than my usual teetering pile of old bath towel or foam bits.
Phil Nelson
Phil's Old Radios
https://antiqueradio.org/index.html