Need Advice] Cat with possible Parvo and wobbly hind legs

Last night my cat had wobbles in his hind legs, lack of appetite, and had 70 breathes per minute (his breathing is normal now tho).

His brother died last Sunday because of Feline Parvo and FIV. So I was scared that he also caught Parvo.

My cat doesn't struggling peeing and still poops. His poop has form, just a bit mushy. He poops once every night and morning.

I brought him to the vet today to get him checked. They did a CBC and the results are on the picture. The vet said he had an infection and because of exposure to his brother it was probably because of Parvo. I didn't go for the Parvo rapid test kit because I didn't have enough money so we assumed it's probably Parvo.

The cbc results are all normal within range. Except for this: NEU# is 14.45 10\^9/L and ref range is 1.8-12.6, while LYM% is 0.099 and its ref range is 0.1--0.530. I can't attach pics.

I asked about the wobbles in his hind legs, and the vet said that it was probably because of the infection and pain he's in. She said it could not be a musculoskeletal issue otherwise there should be no infection. Is this right?

I also asked about the fast breathing because I was worried I might have accidentally put fluid in my cat's lungs when taking medicine. But the vet said that it could not be that. She said pneumonia would show very severe infection on the CBC. Is this right? Did I ask it wrong?

Her prescribed medicine are:

1. Amox + Colistin (CANIXETIN)

2. Immunol Tab

3. Dextrose powder

We're scheduled to come back for a follow-up CBC next week.

I know vets know better about pets than anyone but I'm just scared I'd lose another cat. I want confirmation. I don't have enough money for various tests so I want to confirm this. My cat still has wobbles now. Front legs are fine tho.

Medical History:

My cat had stones in his bladder months ago and he struggled to pee. Thankfully it's cleared now. He takes nefrotec tablet as maintenance twice a day.

Could I be missing something? Am I overreacting?

Poster Age: 21

Country: Philippines

Vet info:

Main issue: wobbly hind legs

Cat Age: 1 year 10 months

Sex: Male, not neutered

Financial situation: Can't afford expensive lab tests