Well, the good news is I gave Jake half of his appetite stimulant pill, and he wolfed down everything I put in front of him (which wasn't an excessive amount as I want him to continue to be hungry and eat) and I'm hoping he can go pill free from now on. He even ate the food with the L-Lysine in it, which he wasn't too happy to do the day before. His breathing does sound a lot better, and I got him to purr for quite a while last night with nary a cough, so that's comforting. He's also shown signs of his voice coming back. I hate to jinx myself, but it does seem as though he's on the mend!
Those are some great tips for getting him to chow down - thanks to both of you! Hopefully when his sniffer is back in action, he'll eat whatever I give him - he'd never been a picky eater before, so I really think it was just the cold and the antibiotics that have been bringing him down.