The CPR should be fine. I've never used it so just be mindful of how your hair feels after you rinse it out. If it doesn't feel soft and strong then you may need to follow it up with a moisturizing conditioner.
One time heat damage would be all that it takes but the degree of damage may vary. Your hair could be weakened and manipulation would cause it to break or it would break on its own. I'm guessing heat damage since you said it was long pieces without the bulb which would coincide with where you put the 430 degree flat iron on your roots. But don't panic and don't think about cutting your hair just yet. I had the same problem a few weeks ago (lots of shedding and breakage - I thought I would be bald - but I'm also on medication so not sure if it was all BKT).
I BKT'd again after 2 weeks from the last application and my breakage has reduced greatly. Three things I made sure I did - (1) I clarified twice and the second time I left the shampoo on my hair for 10 minutes (Pinkskates tip). Something I hadn't been doing. The clarifying shampoo is suppose to open the cuticle layer to allow the BKT in and I started skipping it all together
You must clarify. (2) I made sure I applied the BKT from root to tip using small parts. My hair was wet with the BKT. I know some are saying to use less but I think my version of less left some of my hair untreated so when the flat iron was applied it was on my hair and not the BKT. For some reason, I'm no longer irritated by the Softliss fumes
and I'm careful to keep the hair out of my eyes, nose/face so applying more this go 'round didn't bother me. (3) I flatironed at 410.
ETA: Split ends? Can you see them? Snagging doesn't necessarily mean split. Your ends could be dry or could have come into contact with the fabric of your clothing and tangled. Whatever you do, always be gentle when you comb and never force your way past a snag. How often are you moisturizing your ends and with what? Also, I don't have a pibbs but you shouldn't sit under any dryer for longer than 1 hour and consider spraying your hair with a spray oil every 15-20 minutes when you do.
Keeping my fingers crossed for you!