Yes, I agree with your regular vet's recommendations. When you first mentioned Milo wasn't eating, I had suggested there was a strong chance he could have developed hepatic lipidosis, as this is the way the cat's liver reacts to not having food to process for 48 hrs. or more.
From your description of Milo's symptoms to the emergency vet, I'm surprised they didn't first treat him for heaptic lipidosis with nutrition, fluids and antibiotics. Did the ER vet explain to you why they chose to do an exploratory? The "nutmeg" appearance of the liver may be a result of lipidosis, and I've also found information indicating that ingestion of lead may cause this condition. Have you done any renovation around your house recently, which may have caused lead paint or any other substance containing lead to have been present and possibly ingested by Milo?
If Milo remains in the ER vet hospital at this time, what treatment is he currently being given? I'm assuming, IV fluids, IV or tube feeding nutrition; any medication? Did they biopsy the liver when the exploratory was done? How is he doing now, recovering from the surgery, etc.? Is your regular vet in contact with the ER vet?
"In chronic passive congestion, the liver is slightly enlarged with an irregular or granular capsular surface. When a cut surface of the liver is examined, the congested centers of the lobules contrast with the relative paleness of the peripheral zone. Thus, the congested liver looks somewhat like the surface of a "nutmeg" cut in half, hense the term "nutmeg liver." (Nutmeg liver is also seen in high altitude disease.) Over a period of time, fibrous connective tissue scarring occurs around central veins of liver lobules (cardiac sclerosis or cardiac cirrhosis). Remember, in so-called cardiac cirrhosis, the essential features described for cirrhosis are usually absent."
From the above description, it sounds like the physical conditions causing nutmeg liver would have to have been present for a while in order to cause such a problem, now, as you and your vet expressed. If this diagnosis is correct, is the vet giving supportive care at this time, or just waiting for you to make a decision? I know how difficult this is for you! Was it mentioned that Milo has any pulmonary or cardiac problems at this time? If so, this could be related to the liver condition.
Please keep me updated on Milo's condition. Thanks! I send my best thoughts and prayers that he can recover from this with the correct treatment!