I just lost my dog after her needing people around pretty constantly. My partner and I can mostly arrange working from home, so the situation is not the same. What is the same is how you approach how your dog feels and how to tell when it's 'the time'.
You're probably the most important part of his life. The shelter might let him find a home that can care for him better or it might not (because people are hesitant to adopt older dogs with health issues). What they can't give is the stability he gets from staying with you. It really sucks that we can't ask them what they want. I know that my pup would never have chosen a longer life if it meant giving us up.
When is it time? There are resources online about how to judge quality of life. For us it was as simple as picking her favorite things to do and watching to see if she still wanted to do them.
I have second guessed myself a lot - should we have done more vet care, should we have spent more time with her, etc. You're in a hard situation. The decicions don't get easier and sometimes are no win. My advice is to make your decisions for him as best you can knowing that your best is not ever going to be the perfect ideal AND it will be good enough.
'Ask for more' is different from 'Get more'. The labor contract is a negotiation. Ultimately, the only card unions have to play at an impasse is a strike. If they use that tactict the workers of the union won't get paid while the contract is unresolved.
Let's say you're supporting your kid, don't have savings, and are offered a raise and some meager time off. Do you feel like you have the freedom to push harder, ie go on unpaid strike longer, or do you vote to accept the deal and get that paycheck again?