i like those triple supplies from rigol. its much like the siglent you posted, but the 3rd channel is not fixed. its also fairly easy to script it with python. dp800 series.
yes i think so, but u would have to make sure the solder will rise through the through-hole as mich as possible. maybe u can try to find the faulty pin with wiggling them separately
pressfit connections usually are very reliable. if there is a poor connection i would presume that the barrel of the via is broken and a new pressfit connector will not help. maybe putting solder in would help. did you already test for poor connections?
usually fans have a min start voltage. u can try if your fan starts at 5v and if the resulting RPM is ok for you, just solder it without any resistor on USB
i assume its measured under laboratory conditions, so it seems ok to me. TCXO, OCXO should usually be operated within their operating voltage range. depends on type. usually i would assume 1.8-3.3v, but who knows without datasheet?