Integrating a 7 month old rooster

[The Zoo]

I need to integrate a 7 month old rooster back with his flock of 3 hens (he was accidental). I removed him because he was too hormonal and was roughly mating the hens and two were injured because of it.
He currently is living in a large wire dog kennel and I have let him out a few times with the younger hen who likes him and they still get along just fine. She also gets along just fine without him.
My coop was built for 4 hens not 3 hens and a rooster so it's on the smaller side but soon they will have access to a run with a lot more room.
I am thinking of building him a bachelor pad for in the run where he will spend his time when he can't be monitored and so the three ladies will have a safe area to get away from him.
I would love to have all four getting along and living together eventually and I'm hoping this will happen when he is no longer a teenager or his rooster skills get better.
Any and all suggestions are appreciated. I hate to have to put him down because he's being a rooster but I can't have him injuring my girls again.

 

[Cloverleaf Farm]

Was he just scratching up their backs? If that's it, then you could put aprons on them. I had to do that with mine because my roo rips out their back feathers. Works great, and gives the big boy something to hang onto!!

If he is injuring them in other ways, it may not be worth it to keep him...or maybe trade him for a smaller roo if you want fertile eggs...???

 

[The Zoo]

I did buy chicken saddles (very cute skull and crossbone ones for the older girls and a pink one for the younger). And I use them and they work great.
The injuries weren't technically his fault - he was trying to mate with the 2 older girls, they stuck their heads through the wire we have around the pen and they ended up cutting their necks pretty severely (we have since put netting up around the coop so they can no longer stick their heads through it). They just really don't like him very much. They're used to being top chickens and were very used to his being 3rd on the pecking order. He's trying to take over the top spot now as he should. He is very good with the hen who was raised with him, is her laying coach, gives her treats, etc. The older girls he just chases around till he jumps on them. He has tried dancing for them but they're not impressed.
I don't really care about egg fertility as I'll never try to hatch them. I didn't want a roo, he was one of the 'day old chick 90% chance of it being a hen roos'. He's gorgeous though and so far nice to dogs, cats and people so we'd like to try and keep him since I've had no takers on rehoming him. Everyone seems to have all the roos they want.