I Have A 14 Year Old Rescued Male Cat With

I have a 14 year old rescued male cat with multiple health issues including feline herpes which has atacked his corneas (he's had a conjuntival graft in one eye by a BC Veterinary Ophthalmolosist. He's on Viralys powder and cidofovir and idoxiuriding eye drops and the local vet has treated him with Clavamox for a UTI. He is VERY congested, difficulty breathing through the nose due to congestion and now seems over the UTI but is snorting and and snargeling (excuse my vocabulary), but eating and taking water mixed in his food. Local Vet thinks he's probably allergic to something and has prescribed a dexemethasone injection but I'm asking him about acyclovir for a herpes flare -up and he's agreed to order this, though doubts it may be useful since not FDA approved for cats with herper. Appropriate? Other ideas?