I have been recommending it, I do it a lot, it does work for most roosters, but it doesn't change a bad rooster, just gives the good ones a chance to calm down and mature, letting the hormonal stage pass and the hens to mature, which your rooster is, is hard to say, but I would separate him...
I have 11 roosters mating hens all day, never do they rip open the back of the head, that requires cornering and repeatedly pecking, not done during mating in my opinion, just my 20 years of chicken keeping opinion. Enough said.
That was more than rape, rape in chickens is when the rooster sneaks up and grabs her and she screams, he does his deed and usually runs off, maybe pulling out feathers, what yours did was an attack, way different, rape is either a young rooster thing or a not so nice rooster thing. Most hens...
this is why I don't buy at the tractor supply anymore, that's a bit too much aggressive behaviour from that rooster towards the hens, I would not bother with him and make other arrangements, but if you want to try keeping him around I sometimes lock a overly amorous rooster up in a separate pen...