Thanks Joe. So as suspected, there's nothing wrong with applying the H&R springs up front, just a loose nut behind the wrench.
What made my miev into a rattletrap were the front swaybar linkage nuts. The ball-joint studs that secure these nuts have an allen key socket, so you can steady the stud while torquing the nut, but that prevents the use of a normal torque wrench. Turns out, the ball joint starts spinning in it's socket right about the time the torque wrench wants to click, so a shadetree mechanic may have no clue that his nuts aren't torqued right. That explains why the rattle was bad with any tiny bump, yet the swaybar seemed firm to hand pressure. The studs then loosen up quickly if insufficiently torqued, and only about 30 miles after a visual re-inspection and firm hand pressure on the swaybar, one nut had vibrated loose and completely fallen off! Luckily, the stud's threads weren't buggered up, and a scrap Toyota Corolla swaybar linkage had the same nut...
In short, my struts now seem fine with the lowering springs, the front end is 1 1/2" lower, and anything from broken pavement up through speed bumps feels much more civilized than stock. Cornering feels much more confident. I wasn't able to measure any camber change with eyeball or iphone inclinometer, but intend to put the car on an alignment rack once I 'finalize' the rear end setup. (Though there is no front camber adjustment mechanism- would have to go custom.) Bottom line- if you have an annoying rattle in the front end- check the swaybar studs! The two nuts mounting each strut top to the fender never worked loose, and same with the bottom two strut nuts and the top nut on the strut's piston.
Rear suspension still has 3/4" plywood spacers, will revisit that later. I haven't decided whether to make permanent spacers out of something solid or elastic, and may add a bit more thickness to prevent CV joint rumble at full load. The rear springs sure smooth out bumps better than stock, so I wanna keep 'em even if it means stock ride height.