I'm going to give as much detail as I can possibly remember off the top of my head, but please feel free to ask questions if you think I left something out.
Ten days ago, my mother brought home a small Eastern Gray squirrel. She was driving and the squirrel ran in front of her car in the street, and she stopped to let it pass. However, he ran under her car instead, so she got out and called it over to herself. He didn't hesitate at all, and came right over. He seemed happy and healthy but she was afraid that with that level of trust, he wouldn't last long with the dogs in the neighborhood (which often roam freely). From her internet research, she estimates him to be about six weeks old when she found him, so about 7 weeks now. We don't have any instrument with which to weight him, unfortunately. All I can say is that he is small, fully-furred, eyes open. Rough estimate, he's about five inches long when sitting up, from nose to base of tail.
She brought him home, and then sped off to get some supplies for taking care of him. It's at this point that I'll mention the house has been a veritable zoo for the last 20 years - dogs, cats, a rat, four chinchillas, three mallard ducks, two turtles, and a dove which I found walking along the sidewalk outside of our town's bank twelve years ago (he's one of two animals still with the household until Chester, the squirrel, who makes three).
She came back with Esbilac Puppy formula and some syringes for feeding him, along with some bedding for a cage we already had. We began by feeding him the Esbilac, which he enthusiastically sucked down his first day or two. After that, he wasn't as enthusiastic about it, and began to refuse it altogether by Day 4. We switched to a goat's milk/heavy whipping cream/yogurt combination, which he enjoyed, and kept him on that until the Fox Valley 50/20 arrived on Day 6. We transitioned him over to the FV over the course of four or five feedings, and he enjoyed it. This is currently what we're still feeding him.
On Day 3, he was brought to the family vet who used to look after the chinchillas, and still looks after the last remaining cat. She is considered an "exotic vet", but Chester was only the second squirrel she'd ever seen as a patient, and she admitted that she wouldn't know much about them, but agreed to examine him anyhow. Because he had been sneezing and the expelled mucus was pink, she believed he had a respiratory infection and prescribed Sulfatrim to take care of it. We've been giving this to him at the prescribed amount of 0.1ml, two times a day. He does not seem to be sneezing blood any longer. Other than that, the vet cleaned up some blood that had dried around his nose and he was on his way back home.
On Day 5, I noticed something else was wrong - he was moving around, but avoided putting weight on or using his front left paw. I told my mother, she saw it too, and that was when she told me that the day before, she had accidentally kicked him when he ran between my mother's shoe-clad feet. It was enough that she felt Chester's body being hit by her shoe, but only seemed to daze him and he continued running around like nothing had happened. On top of this, he had another potential injury, as on one of the previous days (Day 3 or 4), he jumped from my shoulder after slipping free of my grasp while I was holding him, waiting for my mother to get one of his feedings prepped. He landed feet-down, but appeared to have landed flat (all arms flat against the floor, belly down). Again, he was dazed, but seemed otherwise unhurt.
Since Day 5, his symptoms have gotten worse, and we suspect that he has MBD. My mother had done additional research and found the he needed sun exposure (or full-spectrum light) to be able to absorb the nutrients in whatever we fed him. It wasn't until Day 8 that we realized this, and up until then, he had spent most of his time being held by my mother in a blanket (fully covered). I made a dash to a pet store in the nearest city and bought a full-spectrum light, the Exo-Terra Reptile UVB 100 (26W). This was installed in a dome-shaped reflector dish lamp, which was then set on the top of Chester's cage. He has been held a little bit each day since then, but has spent the majority of the time underneath the light, in his cage. Most sources I found, including on this site, indicated that squirrels only need 20 minutes of exposure to this light each day. That really seems wildly insufficient, and the vet believed the same as I, so he's been getting several hours a day for the last two days (with shelter provided in his cage if he needed to escape it).
Symptom Progression Chart
Day 1 - Seemed to be sneezing a bit of blood, had some crusted on his nose.
Day 3 - Sees vet, who prescribes the antibiotic, but otherwise believed to be in good health.
Day 5 - Noticed reluctant use of front left paw, otherwise active and running about the house.
Day 6 - Almost no use of FL paw, new reluctance to use FR paw, becoming somewhat lethargic. Now seems to keep both eyes open all the time.
Day 7 - Little, if any use of front paws; lethargic.
Day 8 - Back paws showing signs of "splaying"; more lethargic than previous day.
Days 9 & 10 - Barely moving, whether being held or left in his cage. Frequently seems to move by rolling instead of stepping or walking. Occasionally closes eyes now. Still eating hungrily each time we feed him. Has begun biting fingers - never broken the skin, but still a pretty firm bite.
Feeding Chart
Days 1 - 3: Esbilac Puppy formula; 10cc, 4x daily, decreased appetite on third day.
Days 4 & 5: Fed goat's milk/whipping cream/yogurt combination; well-received.
Day 6: Transitioned over course of the day from goat's milk formula to Fox Valley 50/20; also well-received. Still feeding 10cc, 4x daily.
Days 7 & 8: No changes.
Day 9: Began crushing and dissolving Tums tablet* into formula, increasing frequency of feedings, reducing quantity per feeding to approximately 7cc, 6x daily. Appetite still good.
* Tums 750, which contains 320mg of elemental calcium, according to this page. Crushed into powder, approx. 1/4 discarded to get closer to 250mg recommendation for a young gray squirrel. Mixed into formula and fed over course of the day.
Waste Chart
Too sporadic to list by days. Urinated freely and easily up until today, Day 10. Fecal matter has been very limited, but last described as soft and yellow.
Additional Notes
-Has not seemed to have gained any weight since intake.
-Has been offered fresh twigs from the apple tree in our backyard, with no interest.
-Has been offered small pine cones, which he shredded (but did not necessarily consume), as of a few days ago. Currently, no interest.
-Has been offered squirrel blocks, also without interest.
-The little time that he has spent running around the house was limited to the living room, kitchen, and hallway; usually supervised wherever he went. Has not chewed any cords or furniture.
Have we made an error in our diagnosis? Is there something more we could be doing for him?
Please note, we unfortunately cannot afford to have any x-rays or lab work done at this time. We know this is a major complicating factor, but it's where we are.
Thanks in advance for any help.