Expressing worry about brittle pieces involving Mixels + Some questions

So, just earlier I've deconstructed my Mixels Infernites max back into their base forms (Flain, Zorch, and Vulk) and guess what? Most if not all of the dark red slope pieces were cracked and one even broke.

I had to throw away almost all of them and replace the ones with the replacement pieces I've bought off bricklink and one I've got from Lego's Replacement Service. But I'm starting to worry those replacements pieces might be brittle too, since I might be seeing tiny cracks at the bottom front slope part of the piece, but that might be my eyes playing tricks on me.

Lastly, I am starting to worry that every other pieces of the Mixels line might be brittle with age, call me crazy but these sets are old, and the pieces might get brittle over time making doing their intended use of mixing them together kinda anxiety inducing because I might unintentionally break a piece or two.

I've got a few questions to close out.

1. Is there a cap to how many pieces you are able to take from Lego's Replacement Service before you have to pay? I've heard somewhere that Lego might make you pay for replacement parts if you order too many parts from their service, but I am not too sure.

2. Should I be more gentle with my Mixels when taking them apart? I really want to do more with these guys since their main purpose is to be mixed together to create all kinds of Mixes, Maxes, and Murps. But with the whole threat of their parts breaking or becoming damaged looming over me, I am wondering of some ways to play with them and take them apart gently without damaging their parts.

Thank you!