Don't forget the line from that message in a bottle vision Dalinar had - "If only all spren were as discerning as honor spren".
Also, I think at this point the main difference between Dalinar's sons and Elohkar is when the former king started to change, people started talking. Elokar would have heard that, and probably before he could start trying to imprint his new values into his son, the old king died.
Dalinar at this point has had years to bring up his sons "correctly", and Elohkar was thrown right into being King after his dad died.
As for him being jumpy - don't forget he IS seeing spren (whatever their origin, although they do seem to match the descriptions of cryptics), and the only person that might have figured it out has apparently spent the entire time since he has started seeing them away from him. So as far as everyone else is concerned, Elohkar is going mad. Which would also have a negative impact on him.
