My girl Ratatouille had a PT. I had her on Cabergoline and had to spoon feed her baby food and syringe water for her every 3 hours, luckily she didn't refuse meds, food or liquids until she was full. If you have trouble keeping him hydrated I used fruit to help. I picked up assorted fruit bowls(watermelon, honey dew, etc.) and diced it bite size for her and she went crazy over it. I used small jars of babyfood and dipped a plastic spoon in and let her lick the spoon clean.
I was just like you asking myself if I should let her go, when will I know to let her go, how will I let her go etc. it was definitely hard for me but when the day came when she could no longer eat or drink her special diet and I knew she was going to start suffering from dehydration and starving I contacted my girlfriend and she came home, we spent an hour or so with Touille and said our goodbye's and euthanized her at home. I don't suggest home euthanasia for the simple fact most people are not equipped to complete the task humanely and affectively like us, as my girlfriend is a veterinarian.
If you have any more questions I will be glad to help. Hope your sweet boy is doing well considering.