I've been growing icebox size watermelon (sugar baby and its hybrid cousin tiger baby) in a 25-gallon half whiskey barrel for the past five years, and it works well in my situation. I plant my seeds indoors and transplant them very gently when they have just formed their first true leaves and daytime temperatures are reliably above 70. I've grown four or five plants in the barrel and gotten an average of two watermelons for each plant. I did try trellissing them, but as soon as I see the melons begin to form, I gently rearrange the vines so the fruit is resting on the ground or some sturdy platform. The vines still range over the trellis, which is very pretty, but eventually they climb out of the pot and extend a few feet out from it on the ground. My melons are usually around five pounds, which may be a little smaller than ones grown in the ground, but they are so sweet and clean. The planting mix I've been using is the 5-1-1 they talk about in the Container forum. It's five parts pine bark fines to one part each perlite and peat moss. My situation may not be ideal, but I can't grow melons in the ground, and this works well for my small family. Here's a photo from last July. And here's one from June, a year earlier:

To be honest I've only really observed tupelos for sale in containers, rather than mature ones. But for ones I've seen for sale, this leaf size is if anything slightly large. But I think this happens with some plants (grown from seed). When I planted mine it was a spindly 3/8" caliper, 4' tall tree that was under potted. Now that it is about 7' and has a thicker trunk, maybe 2", the leaves are getting bigger. It hasn't grown up that much, more out. I suspect it is has been developing a tap root since I do not water it. In the coming couple years I expect some improved vertical growth. It's maybe 5 years old at this point.

Would Nyssa ogeche be available? Obviously Nyssa sylvatica is the most available... But the berry color doesn't match yet.

I'm trying to build my soil and I have read stories where even the hardest clay changes simply with top dressing every year. It takes much longer this way (years), but the stories have been convincing. I'm leaving the autumn leaves in my garden and I take bags of leaves from my lawn and keep them rather than giving to the county. I try to shred the leaves but we find the process messy and unpleasant (loud shredder) but I usually get a bag or two done which worth about 5 bags unshredded. I use the shredded leaves as a bottom layer of mulch for my vegetable garden and any leftovers for my ornamental garden. The whole leaves are used for the ornamental gardens and back "wild" garden. On top of the leaves, I put shredded hard wood mulch for the ornamental garden and natural bark mulch for the vegetable garden. I use much less than if I only used mulch as I have the (completely free) layer of leaves underneath. My vegetable garden gets turned a bit every year as I plant new, so I have seen the best change in my soil as the broken down mulch from the previous year is incorporated into the top few inches as I break up the soil and create a smooth planting base in the Spring. I'm starting to compost again and hope to have my own compost to use as another layer. My county doesn't do this, but others nearby will deliver for free to residents truck loads of compost (I'm so jealous). You might want to look into your local services to see if they either deliver or allow pickup of mulch or compost for residents. I'm really excited for you and your project! I think you will have an amazing woodland garden!