my suggestion for the squat rack, is to make the wood shorter, so the bar is much closer to the uprights, and reduces the leverage on those skinny bits of metal and their welds.
ie, put the screw a few inches away from the upright, not a whole foot
other concern would be with re-racking.. if you trip forward with a bit of force, the whole lot could topple over??
would also consider a clamp of some kind, or a bolt thru the wood and each upright, to give an extra smidgen of safety (although drilling thru the metal uprights will weaken them a bit)
for the bench safety stands, i'd be a bit worried.. they need to be stable both sideways and forwards/backwards
i'd try to either bolt them to the bench somehow, or bolt to the floor if possible.
i figure.. if you can load your equipment up more than you can lift (say, 50%) and then PUSH the stuff around and it is still stable and looks safe (no wobbles, doesn7t fall or buckle), then good to go.
you could make squat safeties and bench safeties out of wood like in that first vid. 2 or 3 bolts, good thick wood..