He needs to get to a vet asap. His droppings are abnormal and show signs of a budgie who has not been getting enough to eat recently, probably because he isn't feeling well (the green tint around the urine). Have your vet do a crop smear and fecal smear to check for bacteria, yeast, and megabacteria.
Since he is showing heavy signs of illness (sleeping a lot, not talking, not drinking and eating as much, being very close to you in ways that he isn't normally and vomiting, which is the neck jerk), it means that whatever illness he has is progressing. Birds are experts at hiding illness and only show their symptoms when they are already very ill.
Until you can get him to a vet (which should be today or tomorrow), make sure that he has a warm place to nap - unless it's 40C near his cage. Birds have a higher body temperature than humans, and if he is puffy, it means that he's trying to retain heat.
Give him probiotics in his food or directly (I use Harrison's Booster, but perhaps some other members can chime in on their successful probiotics). Keep a weight diary using a kitchen scale. Feed him egg food (hardboiled egg cooled down with seed, millet, flax seed, and his favorite veggies) to try to keep his energy up, or soak millet in pedialyte or rehydration fluid if he won't eat the egg food.
I would speak to your vets about a payment plan or about other things you can do to work off the payment (like volunteer to walk kenneled dogs or clean up) if you can't afford the visit.
Best of luck, and we are hoping that your budgie makes a fast and full recovery with your help.
PS - You can see how to make a bird first aid kit here for future reference, so that you will always have the best things right on hand: https://talkbudgies.com/emergency-roo...t-aid-kit.html