You can also move her to the roost in the dead of night. She won't get off of it in the darkness and she'll wake up there in the AM. I think this helps for broodies too.
Hey Hey, let's see some pictures, we all like pictures of Rhode Island Red chickens & Ducks.
I have one production RIR, she lays a massive brown egg about daily.
If he's gonna make it, he'll absorb it. All you can really do is provide food, water, warmth. Keep away from other chicks if they're messing with him.
If he's acting pretty lively and eating/drinking, he should be OK.
Likely, just waiting until they self amputate will be OK. If you amputate you'd need to do it through healthy tissue and you might just create a greater chance of systemic infection. Certainly monitor above the site for redness/swelling in case you need to rethink or introduce an antibiotic...