11 week old kitten with a really bad URI please help

11 week old bsh

took him to the vet a couple times alr (once on wednesday and once on friday, today is sunday and they're closed) and they said he has a upper respiratory infection. tested for what kind of infection it is but results dont come back til next week so they don't know what meds to give him (also he's really small so they are worried to give him a lot of the types of meds) but they prescribed him Doxycycline 25mg/5ml on friday and he's been taking it once a day but he seems to be doing worse and worse :( his symptoms started with teary eyes and sneezing lots but his eyes are getting more and more swollen and it seems like today his nose is clogged so it's harder to breathe. in the mean time i gently clean his eyes with a warm compress (using heated up bottled water since i heard tap might have bad chemicals) and since he just started getting congested im going to play with him while the shower is running so hopefully the steam helps. i have a humidifier in my room but it doesn't seem to be helping much. he eats a lot and uses his litter box fine. don't come at me saying he should still be with his mother bc his old living arrangements were horrible and i saved him from the trenches

i guess i just wanted to ask if there anything else i can do in the mean time? he seems so in pain and idk how else to help him :( would love to hear any of your experiences with young kittens with URIs

i researched a lot and saw a lot of people saying their cats started getting better after ~5 days on antibiotics but that seems like a long time of suffering :(( i'm a first time cat owner too so im so worried. any advice will help thank you in advance