To answer some of your questions:
Yes, some IV drugs can be scary if not administered properly in appropriate doses. Maybe it's protection of the RNs, but I strongly suspect more comes from the hospitals own liability insurance
. As an RN I routinely push narcotics (have actually only hung an IVP of a narcotic once... relatively recently actually) and anoxylitics. The view is probably that the RN has more educational background in med admin than an LPN and SHOULD (do not read into this, it's not necessarily the case) be more cognizant of the risks associated with certain drugs. The RN doesn't make me inherently safer, but for insurance purposes it's probably cheaper to say that only RNs can do it vs RNs and LPNs. To be honest with you, I was an LPN once and I've known some very good LPNs who I would have no issue with having them push IV meds. I've also known two RNs who have killed patients because they were simply incompetent when it came to this stuff. It's too easy to do if you're not careful.
There is no "IV cert" for RN's, it comes with the program that you attend and passing NCLEX-RN is viewed as a general competence to give IV push medications (as scary as that might sound).
I would NEVER discourage an LPN from getting ACLS and PALS, having them does two things: 1) it shows that you are capable of getting through the course which, for many people is, very difficult, and 2) it exposes you to scenarios and information which should make you a more competent provider. Knowing rhythms and being able to predict consequences of said rhythms would probably be the most important take away that an LPN would get from those courses. That being said, you should never be in a position where you are pushing lidocaine or magnesium on a coding patient as an LPN, because simply put, if the outcome isn't good the families lawyer is going to have a field day with you, the doctor, and the facility.