Droppings aren't like a starvation look (that bright green) so something was getting thru. White and a moss green color, kinda loose though.
Is not coccidia, that would make the droppings shapeless, mucous or creamy-aquous, without white part and often smelling bad and strong (you can see a photo on the "Chronicle ..." thread).
Breathing with noise can be caused by several things:
-bacterial disease (giving Doxycycline is usually the best)
-mites - give Invermectin
-aspergillus - give Itraconazole or better, Voriconazole (very expensive). Treatment lasts long
-canker on respiratory tract or pushing on respiratory tract
-worms
If you can't afford lab tests, the only solution is to try one one by one medicines for each one of these, with a pause of 12 -24 hours between them and see if appears any improvement. But giving so many toxic substances will inevitably:
-weaken or kill the bird
-make the disease advance if you don't hit it soon enough.
The blood, according to this table, can be caused by Hexamitiasis (a protozoa), Salmonella (bacteria), E. coli (bacteria), worms or coccidiosis:
http://www.chevita.com/en/pigeons/symptoms
So you may try an injectable antibiotic (lincospectin is my favorite) maybe also a dewormer, while keeping the treatment with metronidazole, ideally by injection, 5 mg / day for few days. Look for this human product:
http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=fd191c06-9d3b-4e46-9f79-90f6af614947
If you use this, you have to buy a bottle and throw it after for each administration (the substance doesn't resist after opening the bottle).
Giving injectable the medicines is more efficient (the substance enter the system better) and is preferable in such cases as canker, when lumps can block the digestive track.
The fact that vomits may be because of crop blockage. for this, fill the crop with like 10 ml of water using a syringe and tube and then massafe the crop to fragment the food and especially to remove the food on the body wall, where is the channel communicating with the gissard. Massage that area untill you feel no food is felt there, is very important. Don't try to take then the crop content outside, is very dangerous.
Then, feed the bird with a mix of 2 parts water and one part honey (like 5 ml) 3 times a day for few days.
And keep the bird on electric pad or other warm device, in a dark and quiet place, without air drafts.
