What about
Ashley or
Sally for
Asa? I agree, you'd better do something! The other girls should be fine.
Stian is interesting - is it from
Christian, or
Sebastian, or something else? Maybe the full form would be safer, otherwise it might look as if he had a girl's name like
JoAnn.
Frode is very Tolkien!
Bo could attract trouble but I'm not sure what to suggest - wasn't there an actress called
Bo Someone? But the French
Beau is as masculine as can be. Might be OK. And no real problem with Ulaf, except that you get being pronounced ; if that's the worst that ever happens to him, he's a lucky young man.