Hi there again
About peas: they don't need support but small sticks in the ground next to the plants to give them something to twine on will help keep the pods off the ground. Legumes don't need much nitrogen, they are capable of making their own but will appreciate the minerals available in mulch. Peas like regular water but well-draining soil.
Seeds are not viable for too many years so don't save them thinking they will last, better to sow fresh seed.
I just make compost heaps, sun is good because the hotter your compost, the faster it breaks down although a heap should generate its own heat once breakdown is in full swing.
About the neighbours: you need to fix your fence to keep the rabbits out, they are the main damagers of your crops the squirrels need a ferocious hunter of a cat to keep them out of the yard. I don't have squirrels where I live but plenty of large rats and my cats keep them at bay