Just my personal thoughts on your questions -

• Our rule is if you bring it to the park, you will share it. If you don't want to share it stays in the car/bike basket or at home. My son (4) generally wants kids to come play with his toys, he wants kids to play with him. If he gets very sensitive and starts guarding the toy, he has the choice to adjust his expectations or put the toy away. When another kid has a toy, our rule is that we ask permission before we touch it.

• I no longer have a dog, but I think it's unreasonable, unsafe and in my town possibly (hopefully) not lawful to tie a dog up at the playground. If you have a dog in a public space, you need to be right there holding the leash and supervising it. If you don't want to do that, take your dog home. I don't let my kid approach strange dogs.

• I intervene in anything at the playground as little as possible, preferring to let the kids settle it. If they seem to need help I get involved, for example if I see that my son hasn't asked permission for a toy or is being grabby. But in general I just watch to make sure my kid is being well mannered.

• In my area, I have had consistently good experiences at the parks and most parents seem to be more or less on the same page with this. My one issue is parents who have really young kids (new walkers) on the big playground equipment where the bigger kids are playing, and have unreasonable expectations about the other kids keeping distance. Definitely I don't want my kid to push or scare littler kids, and we value and work on gentleness, but if your kid can barely walk without you holding both their hands, the playground is not yet really appropriate for them - at least on a Saturday afternoon. I value inclusiveness but I hope we all have a reasonable sense of what to expect and how to behave.