I heard the real reason why Cain murdered Abel was because Abel made fun of Cain's big toe?

I don't think it was his big toe, but his phallus that Abel was disparaging. This, coupled with the fact Abel forced Cain into cuckoldry, was responsible for Cain's murderous rage. Eve had her hands full of apples, not Adam, although Adam was supposedly performing cunnilingus on Eve while she was sampling the apples. This may also be the reason cunnilingus is considered an anointed canonical activity.