Guess I am too old school , Yes I use a thrower-have a few, I always throw Short and trickle up on a beam scale, I do not trust the electronic ones, they might be better now days but they float to much for my liking nor do I trust a thrower to be 100% accurate. One thing I think I noticed in the pictures- primer cratering a bit if the bottom was the first shot progressing up + the other mentioned items to me indicates hot load to start with add heat from unit being fired plus any external heat- hot day, full sun- how long un-fired round sat in hot chamber- things can go south quick.
Never heard of bullet weld before but maybe that is some sort of local term for a case neck that is too thick for the chamber+ brass + bullet combination.
Stretched case? from expander ball thinning out brass down below- just another thought as I have done that to my self leading to case head separation in a 25-35 long time ago.( no disaster though , just a royal pain to get the case out- TC pistol and I was likely pushing the envelope a bit as well)