Yes you were right to treat him with the ivermectin (spot on) BUT you need to dose him 3 times, once a week to kill off the lice. Ivermectin only kills hatched out adults, and each week a new batch of adults hatch out, so you need to kill them then scrub the cages and everything else. If you have wood or paper-based beddings you will need to freeze them for 48 hours before use to kill off any stowaways in teh future.
As for getting better, that is great! Usually improvement is seen at 4-5 days so you are ahead BUT he is going to need more than 10 days of baytril to get better. At 7-10 days the infection seems to be gone but its not, and if you stop antibiotics then the URI usually flares right back up
You need a very minimum of 2 weeks of abs (antibiotics).
As for getting better, that is great! Usually improvement is seen at 4-5 days so you are ahead BUT he is going to need more than 10 days of baytril to get better. At 7-10 days the infection seems to be gone but its not, and if you stop antibiotics then the URI usually flares right back up