Hello and welcome to the forums!
I'm sorry to hear your budgie is unwell
You're doing a great job taking care of him. I would say he's stressed and weaker than usual, so I think you should give him some millet soaked in electrolyte to keep his strength up. Sugar-free children's Pedialyte works well or you can use a homemade recipe:
½ cup hot water
3 ½ cups water
2 Tablespoons honey (or sugar if you have no honey)
½ teaspoon salt
Optional: 2 Tablespoons Orange or Apple Juice
Mix the honey and salt with the hot water until dissolved
Add the room temperature water and juice and let cool to room temperature before using.
Also, keep him warm and you can cover his cage a little bit. I think he should be fine in a few days if you continue to monitor his scratch and he's eating and drinking.
I understand completely that you don't currently have the means to pay expensive vet bills, but for future issues that could arise, I would suggest setting aside a "Vet Fund" you can put any spare cash in to ensure that your birds can get vet care they need
It's great to have you on the forums! There's no better place to come for advice and I hope to see you around.
If you have any other questions (or pictures of your darlings
), please be sure to post them!