Full name would be [name_m]Calum[/name_m] Kuhn. He would go by [name_u]Cal[/name_u]. Sound okay since he has a full name he could choose to go by later on?
I would use [name_m]Calum[/name_m] straight up as it sounds much better with the last name and [name_m]Calum[/name_m] is short enough that it doesn’t require a nickname.
I think it would be fine
[name_f]My[/name_f] husband wants him to go by “cal”.