It is not possible to say : הוא בחור ?
No. Bachur is older than a boy, it is a "guy"
Another translation could be "Hu Ben"
Well ok but we say even to adult boys... So If I understand well if in this course is used in english boy, it means child - boy.
הוא בן גם צריך להיות נכון
As said in other comments, it could be בן