3 1/2 month old kitten has abscess on tail - pulling out drain. HELP!

Our 3 1/2 month kitten has an abscess above his tail. Most likely this was from a bite from one of the resident cats. I've taken him to the vet who shaved his fur, cleaned the wound, gave time-released antibiotics, and inserted a drain in the wound. Unfortunately, this little boy has become quite adept at removing his E-collar. We've tried two different ones adjusting them for a snug fit that won't choke him. When he had the collar off, he pulled out the drain. Back to the vet to have a new drain inserted. A few hours later, Phin removed both collar and drain again. Will applying warm compresses over the next few days keep the wound from closing? There are just two punctures the vet made. The boy is full of his usual kitten energy, has a fine appetite, and a 10-day does of antibiotics in him. Suggestions to make me feel guiltless about not taking another trip to the vet will be welcomed. Thanks.

The key is to keep the holes from scabbing over to prevent the infection fluid from backing up again causing the site to swell up all over again, but this is unlikely since he has antibiotics in his system, he will likely be fine just continue with the antibiotic.

The question here is, why did he get bit? 

You don't want this to become a regular thing if the resident cat doesn't like him around and bullies him.

Thank you. I think the antibiotics are doing the trick as his ears are cool to the touch today.

As for the biter, yes, that is a problem we are trying to resolve. We followed the suggested practice of slowly introducing the kitten to our older cats. They tolerate each other fairly well, especially at the food and water dishes. I've been trying to help the tabby (who is the agressor) feel more secure and not be afraid of the new cat. 

While it is pretty normal for cats to show the new kid who's who in the home, it is not normal or acceptable for him to be bitten, hard enough to cause an abcess.

Especially with a kitten who is so much smaller/younger, usually an adult cat will tolerate a kitten easier than an adult cat.

Is the new kitten neutered? If not, he MUST be asap.