Welcome
@UrbanGardenerNYC ! I joined National Gardening Association a little over a year ago, and it has been a wealth of information and inspiration for me in my gardening journey. I so relate to your opossum problem, as we have to wrangle with deer, rabbits, raccoons, and ground hogs, as well as opossums. I even once found a 200-pound sow pig in my blueberry garden! A few years back, I was told by a wise older local woman a Native American saying, "When planting your garden, plant 4 seeds: One for the deer, one for the crow, one for the hornworm, and one to grow." In other words, in this natural world of ours, we need to plan to share. That being said, you shouldn't lose your whole tomato crop to opossums - they do not share nicely.
When I was struggling with a family of ground hogs, I tried a wildlife trap. I never trapped a ground hog, but I caught opossums. If your landlord won't deal with them, you can try the trap yourself, but you need to have a means and a place to transfer the trapped animal to, and I suspect that is very complicated in NYC. I finally got rid of the ground hogs by clearing out the underbrush in their den area, and they moved someplace friendlier. Perhaps you can put the chicken wire around the base of the house so they can't get in there? Of course, you don't want to cage them into that space either.
While I was having the ground hog problem, I used a 3-ft tall wobbly chicken wire fence around the garden plants, wrapping 10 inches of the fencing on top of the ground to prevent digging. Still I found a desperate ground hog inside the fence (he got out on his own).
Now I have pursued a new strategy - I provide the critters an easier source of food than fighting with the fences around my garden. I put fruit and veg scraps on the compost pile, and that keeps them happy. I have one possum very protective of that territory, and he doesn't let others come around. However, I don't think this is a good approach in NYC - too many critters and not enough space.
Opossums are not good at climbing smooth vertical objects. Can you put your grow bags in a pot on top of a smooth steel trash can turned upside down? The raccoons could still climb up (nothing short of an electric fence stops them), but the opossums would struggle.
Btw, here is a photo of my critters. The coon is cute; the possum not so much.
