Hi! I was going to private message you but it seems like I can't! From what I've gathered from alumni and also from the interview process, on top of having a strong academic background and clinical experience, they want to know your thought process and intentions behind wanting to do ACNP. If you can articulate why specifically ACNP, then you should be alright.
Also for anyone else reading this, critical care experience is not required! I don't have any critical care experience and during my interviews + talks with alumni, it was made clear that anyone can pursue ACNP if they have the right reasons for it. Hope this helps!