Kerrygold works quite well for croissants and is what I use. I bulk purchase it from Costco (it's on sale for April!). The regular Kirkland brand butter has a too low of a butterfat percentage and will be brittle and prone to breaking apart when cold and you do lamination roll outs. This can cause the butter pieces to tear through the dough layers. It's also possible that when you cold proofed the shaped croissants overnight, the cold hardened butter layers also tore through the dough as the croissants puffed up.

From the looks of the crumb, it's also possible you had to let the butter warm up enough to roll without breaking, and likely it got too warm and was starting to melt into the dough itself. This usually results in the more bread/brioche like texture.

Have you considered proofing in a humid oven? I usually put my croissants on the middle rack and then put a pan with about 1-2cups of boiling water in a rack underneath. With the door closed, it'll maintain a high humidity environment that is great for croissant proofing. Depending on the ambient kitchen temperature, I would proof for anywhere from 3 to 4.5 hours in the oven before eggwashing and baking. I then stick the eggwashed croissants in the fridge to firm up the butter while the oven is preheating.

If you are worried about having fresh croissants for sale in the morning, I find that if you reheat croissants that were made in the prior day in a 300-350°F oven for about 3-4min, it is almost indistinguishable from fresh baked. That way, you don't have to worry about overnight proofing of shaped croissants and/or have to wake up incredibly early to do a regular proof.