How sad for him and for you too
...I wish I had help to offer but I just don't know what to say....It sounds like you're doing all you can right now...
On that cotten ball thing ...I've never heard of that personally and would never attempt something like that......What about trying a vaporizer ? I would check with your vet before doing ANYTHING ....but I sure hope you can make him more comfortable and the best of luck to you.....