Sorry to hear about your pup I hope everything turns out well.
In these cases having a large and fat dog can actually save their lives (all poisonous substances are weight dependent)
Here's what a rescue that I volunteer for puts in every dog folder:
TOXIC FOOD FOR DOGS
Onions: Both onions and garlic contain the toxic ingredient Thiosulphate, but onions are a greater danger. Many dog biscuits contain *small* amounts of garlic. Because garlic contains less of this toxin, huge amounts would need to be consumed to be toxic. This poison builds up the system; it can be toxic in one large dose or with repeated consumption of small amounts.
Chocolate: Chocolate contains Theobromine, a compound that is a cardiac stimulant and a diuretic. This can be fatal to dogs.
Grapes & Raisins: Grapes are dangerous because of an unknown substance which is toxic to dogs – affects canine’s kidneys.
Most Fruit Pits and Seeds: These seeds contain Cyanogenic Glycosides that result in cyanide poisoning, but the fruit itself is OK. (e.g. apple seeds, cherry pits, peach pits).
Macadamia Nuts: These contain an unknown substance that is toxic to dogs.
Bones: Most cooked bones should *not* be given to dogs (especially chicken bones) because they can splinter and cause laceration of the digestive system and/or become lodged in your pet’s throat.
Potato Peelings, Green parts of Tomatoes or Green Potatoes: All contain Oxalates, which can affect the digestive, nervous, and urinary systems.
Broccoli: Broccoli is only toxic in large quantities.
Yeast Dough: Yeast Dough can produce gas and swell in your pet’s stomach and may lead to rupture of the digestive system.
Beer/Wine/Liquor/ Alcohol: Alcohol of any kind may lead to coma or even death.
Human Vitamins: Vitamins intended for humans, especially those containing iron, can cause damage to the lining of the digestive system as well as cause kidney and liver damage.
Persimmons: Persimmons can cause intestinal blockage.
Raw Eggs and Raw Fish : Raw eggs and fish can cause Salmonella poisoning.
Salt, Baking Soda, Baking Powder: In large amounts these can cause an electrolyte imbalance. Severe electrolyte imbalances can lead to muscle spasm or even congestive heart failure.
Mushrooms: Mushrooms may contain toxins which could cause liver and kidney damage.
Sugar-Free Foods: Sugar-free foods containing Xylitol have been found to cause liver failure in some dogs.
Nutmeg: Nutmeg may cause tremors, seizures, and central nervous system damage.
Avocado: All parts of the avocado fruit and tree are toxic to dogs.
Mustard Seeds
Tea (Caffeinated Blends)
Walnuts
There may be other foods that your dog should not consume;
so always ask your vet when you are unsure.