I'm so sorry. In my country we have a saying that goes something like "a shared pain is half a joy", so if it gives you a bit of confidence that you can get through this, know that I too struggle with anxiety and depression and Rutto is having a particularly nasty flare-up today too. We are stronger that we believe ourselves to be, and you are doing everything you can for Squeak. Unfortunately for him, his stone is in a difficult place, and believe me I understand your fear and frustration. I am lucky to have my husband's support, you are in a hard place having to take care of this all by yourself and you're doing brilliantly. If it helps you, I'd suggest writing down a sort of diary for Squeak's condition, medications, food in case some cause him to flare up, and so on, so you have a reference for when you go to the vet, as anxiety can make you forget important details or forget to ask certain questions, or the vet's answers. A blockage is a dangerous thing though, and I'm sorry to say this, but you need to mentally prepare yourself for the worst case scenario. Keep the emergency/out of hours vet contact details close at hand.
We tried a bladder relaxant called Pratsiol for my boys. It's a human medication and it's supposed to relax their urinary tract so it would make expelling a stone easier, provided it's small enough to pass. It was under vet supervision of course. It unfortunately didn't help, but it did its job- they were slightly incontinent during this treatment and needed extra pee pads changes and gentle butt rinsing and drying. You can ask your vet if they think it's worth trying to perhaps make his stone fall into the bladder so it can be removed.
I really hope you can find a vet confident enough to operate Squeak. It's a difficult one. Best wishes