This year I grew snow peas in (2) 5 gallon buckets and then hung them - mainly to keep them away from the resident woodchuck. I did get a pretty decent yield but farmerboybill & flora are right - they will climb on themselves and anything they are near - what a mess! Also, they REALLY didn't like hot weather. Other things I grew in hanging buckets this year - although the plant didn't necessarily hang down: eightball squash - will grow again (and will add more round zukes) pickle cukes - might not grow again as I never had enough at one time to make a large batch of pickles.

Veilchenblau could work. It is extremely hardy and nearly thornless. I have one that is growing up a maple tree. It has long, long flexible canes. From HMF: Mauve or purple blend. Moderate, green apple, lily of the valley fragrance. Average diameter 1.5". Small, semi-double (9-16 petals), in large clusters bloom form. Once-blooming spring or summer. Habit: Climbing, thornless (or almost). Glossy, light green foliage. Height of 10' to 20' (305 to 610 cm). Width of up to 12' (up to 365 cm). Growing: USDA zone 4b and warmer. Shade tolerant.

Keep in mind we're seeing pieces of things, not the complete situation. You'll need to apply your engineering knowledge, too, so as to not create damage that we can't possibly warn you about on account of our lack of seeing what's there. It looks to me like you could shore up the deck structure with various temporary bracing set back from the deck end... as best you can. It might include some angled 4"x4"s and sunch. And once you begin the excavation, you'll need to proceed without delay. some homeowners take forever to get projects done, but it would not be good to do that here. The retaining wall would need to be L-shaped, with the top tying back into grade in order to not suffer an erosion problem from water washing out behind the wall. I wouldn't advice doing just this single wall. I think you need another L-shaped retaining wall at a lower elevation, oriented perpendicular to the main R wall. Of course, any plan like this is brainstorming, not a construction plan. You must work out all the details: wall lengths, depths, elevations, etc. Use stakes and level string on site for mocking up, to help with roughing out some guesstimations

I plant my pumpkins on the top of a slanting hill. I actually caged in my pumpkins 4 years ago as I think if they were able to move down the hill, they’d break the vines. There is a rock wall between my plantings and the grass. I made my own caged area. I have lots of wildlife who seem to enjoy my pumpkins, especially as fall sets in. I have to enclose many in mesh bags to keep from the animals. One year I lost several to animals. They wait for them to get a certain size and eat. It’s late so I cannot take a picture right now.