1) If you have bullets that are loose in the case with only the crimp retaining them you have a problem in your procedure or dies. Because in any caliber that doesn't use a heeled bullet your cases should provide enough Neck Tension to keep the bullet tight enough you need pliers to move it by hand.

What you have described is cases that have ZERO Neck Tension and I suspect that either they weren't sized at all or the flaring die was not set up properly. Either that or you were loading with cases that already had split necks. BTW, I have had cases split when pressing in the bullets and when that happens those cases get set aside to pull the components and have the cases thrown out in the trash. I have never ever tried to get "one last firing" on a split case, it just isn't worth the hassle with extraction and chamber fouling that would result from doing this.

2) ANYTIME you are working with a load that is distinctly light you need to do some testing for Position Sensitivity to insure you haven't created a load that can produce a squib. Personally I would normally consider a load producing 700 fps. to be reasonably free of any risk of a squib with lead bullets but with some powders this may NOT be a safe assumption. As I discovered with SR7625 at one time, the charge tested had enough variation in velocity to produce velocities ranging between 400 and 700 fps, all dependent on how the revolver was held prior to firing.

3) I started out loading with a Lee powder measure and have migrated to the RCBS Competition Powder Measure for a reason. Cheap Powder Measures just aren't worth the money spent on them and the RCBS is worth every penny spent.

4) I do a 50 piece Capability Study on any new powder I'm looking at using before loading one single round. Because some powders just to not meter well in any powder measure and it's best to know that ahead of time instead of finding it out the "hard way". If you have a powder charge of only 3 1/2 grains and the Standard Deviation indicates a potential variation of 1/2 grain it's just asking for a Squib to rely on your powder measure to set each charge. What you should be doing is hand weighing every single powder charge.

5) Finally I have to question your sanity a bit. You had a total of 8 squibs and didn't think it sensible to pack up and head home with the first squib??? The best result of firing into a squib lodged in a barrel is a ruined barrel, the worst result can result in a trip to the hospital in the back of an ambulance.