Here’s the deal.
You basically need to get the bucket set up as a hospital. That means you’ll be fighting ammonia.
The live rock and the macro algaes will definitely do that. But once the bucket is full of tank water you may want to change with some fresh water.
The temp thing isn’t so much about them being a temperate species. At reef temps bacteria will grow and ponies are highly susceptible to bacterial infections, so keeping temps in the 74-77 range does that and most run a UV in thier tanks.
The bigger challenge is to get the stress down and hospital clean.
If the ponie makes through that then you can adress both the feeding and the injury.
With luck the pony folks and
@Humblefish may chime in more precise medication instructions.
The usual pony boards aren’t very active right now.