Wilson's medical needs

This is completely out of character for us to be asking for help. But, I've been encouraged by fellow TD adopters to do so.
Our beloved Wilson (FNA Sam) we adopted at the Illinois transport in Nov 2017. He is our 3rd TD dog. Wilson had been completely healthy and spunky until 2 days ago. He began vomitting on Thursday morning and it continued all night long. He had no energy and appetite. So we called our vet out of concern. They told us to take him to the University of WI vet hospital that night. We took him there, and they were immediately concerned about a bowel obstruction. Abdominal xrays were taken, which showed something in the abdomen, but there was no obstruction.
They recommended we take Wilson home with pain meds and anti nausea meds for the mext few days. Until he could pass what he ingested. So we took him home and hoped for the best.
Unfortunately things got worse from there. Yesterday he continued to be lethargic, couldn't keep his water down and wouldn't eat anything  while on meds.
Then later in the day we also noticed he couldn't urinate. He then also began to bleed when trying to urinate.
So we made the trek back to the vet hospital last night. At which time they could see his bladder was completely full, and his blood results revealed high kidney levels. They said he needed to be hospitalized overnight so they could empty his bladder via catheter and give him iv fluids.
The estimate they gave for hospitalization with testing was $1500-$2000 if 2 nights are needed.
We had to put $1000 down before leaving, and were told we'd get an update the next morning.
The 1st call we recieved this morning, stated that they found struvite stones in Wilson's eurethra so in order to get the catheter in they had to push them up into the bladder.
They said he was doing well and would update us in a couple hours.
At 10 am they recommended a dye bladder test that would show the location of the stones/how many which costs $500. 
However they can't perform the test until Monday. So, they offered to keep Wilson catheterized until Monday at the hospital.
Or they could remove the catheter and if he can urinate on his own he can go home and come back Monday for the test.
We chose to remove the catheter since it would keep the cost down if he can come home. Plus we thought he'd be more comfortable here.
At 11:30 am they removed the catheter and we hoped and prayed for the best.
But at 4 pm we got terrible news. Wilson went all afternoon unable to urinate. 
That means the stones must have travelled back into the urethra causing blockage again. Which means they had to re sedate Wilson and place a new catheter.
The dr is going to try and move the stones again. But he isn't giving us much hope. In fact he is pretty confident that Wilson will need surgery.
The surgery depending on the location of the stones is $2500-$3500.
We can't afford that. We have already spent more than our limit of $1500.
The irony is that we just purhcased pet insurance 1 week ago. And there is a 14 day waiting period. So non of this will be covered. 
We love our Wilson dearly but we have 3 children, a mortgage to pay and other dogs to consider. 
It makes me sick to think that we may need to put Wilson down just because he has stones. In fact if they can get him un blocked he could very likely live a normal life with just a change in his diet to dissolve the stones.
We will need to decide by tomorrow evening what to do. This may be the hardest decision of my life. 
We love you Wilson!
Thank you in advance for considering to help our baby.