Slopes are good places to plant, because water usually flows pretyt well down the slope. You can plant water loving perennials down at the base of the slope so the water doesn't go to waste. One thing to note, if you want fruit, you will need to plant two trees of the species, unless your neighbours have something similar
growing in their yard.
Tk, reading about your trees withering, I'm going talk a bit about watering trees, from my experience and what i've read. It's not anything directly to you lol
Regardless of what type of tree or shrub you transplant, you'll need to water almost everyday to help it establish the first year. Most people water too shallowly and although the soil looks damp, if you stick your finger in the root ball, it's dry. Setting your hose to a trickle, and leaving it at the base of the newly transplanted tree for half an hour will make sure it's water properly and it shouldn't wilt in the mid day sun.