Best I can tell means your hen is heterozygous for Rose comb according to my calculation and current understanding.. making it Rr and the rooster being rr. see if this link explains it at all including how two *visibly* rose comb parents can throw a straight (test mating is the only way to...
Black cross splash is always Blue. You're cute little boy is too.
Both are bantam.. size will be bantam.
Straight is recessive.. so comb *should* be rose.. even if it got only one copy. Looks like somehow this chick got 2 copies for straight/single or no copies for R.. maybe your RC is...