Sorry for the length, here's the Cliff's Notes version: my betta has a few decent sized chunks missing on his back due to injury. He's in a clean tank and seems to be breathing okay. He's upright, but not swimming at all, just resting on the bottom. I need some advice on how to heal him. Any help would be greatly appreciated.
So, my wife and I got a betta as a Christmas gift last year. As a combination of the season and our love for the Cubs we named him (Ron) Santo Claus.
We love him so much!

I taught him to come to the top of the tank at my command by tapping gently on the rim of the tank as I fed him. I even taught him to let me "pet" him. So every night at feeding time I would gently tap the tank and he'd come swimming up for his food and a petting.
Well, two nights ago he didn't show up. I was mildly concerned, but figured he was just being lazy or was busy. It wasn't the first time he's ignored me. I leaned over, saw him and just let him be. Same thing yesterday: *tap tap tap* No Santo. Hmm. Now I've gone from concern to worry. Well, there he is chilling in his top cover. Tonight I tried again.
Still no Santo. Now I've gone from concerned to worry to full-on fear. I ask my wife if she's seen him swimming around the past couple of days. She can't remember. I check and think I see him in his top cover, but now I want to flush him out to make sure he's still alive.
He's not in his top cover! I start to panic and turn the aquarium around and around looking for him, trying to see if he's in his house (a plastic pagoda from some pet store or another). I finally see him poking out of a part of the house. I reach in to nudge him out and I realize that he's stuck. My heart just sinks.
At this point I have no idea what to do. I don't know how long he's been stuck there and I don't know how to get him out. I move my finger towards him hoping he'll wriggle out backwards but that doesn't work. I touch him on his tail hoping he'll scoot out the opening in front, but that doesn't work either.
Now I'm desperate to save him and I grab the house and start trying to break it. I manage to break some pieces off, but I can't break the part where he's stuck. I'm worried that I'm going to crush him trying to break the small area that he's stuck in, and I'm also worried that I'm just going to stress him to death in the process. I finally manage to break it apart and free him. He's alive!
But he's also severely injured. He's got a couple of decent sized chunks out of him about halfway between his head and his dorsal fin. And he's clearly hurt. He's always been super active and healthy and now he's just sitting at the bottom of the tank.
I am wracked with guilt. I was going to clean his tank Sunday evening, but didn't because I was lazy. Same thing yesterday. It makes me sick to think of him trapped like that for three days and that I could have discovered him sooner! And now he's so hurt and I don't know if it happened as he tried to free himself or if it happened while I was trying to rescue him or what. Either way he's hurt, and it's all my fault, and I'm afraid he's going to die. And I'm more sad than I ever imagined I would be about a fish.
So I need some advice on helping to heal him, if he even makes it through the night. I have transferred him to a small, clean tank, but he's just sitting on the bottom of the tank. His breathing seems fine, and when I transferred him his swimming seemed okay. But now he's sitting there. I'm sure part of it is recovering from his ordeal, but what can I do now? Is there medicine that will help heal his wounds? I've read conflicting advice on whether or not to add some salt and even more conflicting accounts about how much. Any help anyone could give me would be... helpful. Sorry about the long post...