You're not being unreasonable. The examples you provided would be frustrating for anyone. You kindly ask him to help out, but he completely disregards what you say and you're left with no choice but to pick up the slack. With 3 young kids and an old dog, the last thing you want is to pick up after your husband too. He should be your partner and help pitch in to keep the house together instead of being yet another person who you need to pick up after.
I would go crazy having the same conversations over and over and never reaching an understanding or resolution. For instance, the spare room with all of his collectibles. He said he would clear it out how many times, and he yells at your to not touch it because you would mess up his system, yet he procrastinates and never ever gets to it. There's a reason he's avoiding it, maybe it's overwhelming, etc. but you need to get to the root of the problem. Maybe you can help him move or organize the stuff to make room for a table in there, like he can delegate tasks to you as you guys work together. If it's a case where you want him to move the collectibles out of the room altogether, where would they go? My husband has a spare room with collectibles as well, and it's not a problem because they're all organized on bookshelves and it doesn't negatively affect our daily lives or routines. What concerns me is that your husband is forcing his family to eat dinner on TV trays in the living room because he values his collectibles over the quality of life for his children.
He procrastinates, delegates takes to other people due to laziness, or assumes if he avoids a task that it will magically get done by someone else. If he's behaved this way for 15 years in this marriage, it will be difficult for him to drastically change because he's probably stuck in his ways so good luck.
Lastly, the health of your dog sounds awful. My family has had 2 dogs, and when they both reaches old age, they became deaf, blind, and also could no longer control their bladder much like your dog. They ended up urinating everywhere, not even squatting but they would just lay down and pee on themselves. All of these signs show that your dog is clearly deteriorating, and when a dog gets to this state you really need to take it to a vet for a checkup. In most cases, when the dog shows these 3 symptoms, the vet will recommend putting the dog down because they are suffering and their quality of life is just awful.