Water it for starters

Since salt seems to be an issue, and people cutting across the yard is also, I would consider a fence of some type in conjunction with the hedge, with the fence on the road side set far enough back that it won't be damaged by snow kicked up by the plows. Unless you use a solid fence, you won't get any noise abatement, and personally I don't much care for the fortress look. I would be more likely to use something like a split rail fence that would clearly define the yard without being unfriendly. With a hedge on the yard side of the fence, it will be protected from foot traffic by the fence until it reaches a reasonable size, be farther from road salt, and add beauty. If you don't want a permanent fence, at least use a temporary fence such as a mesh string trellis on stakes to protect the hedge until it reaches a size to discourage those who cut across the yard. I love panicled hydrangeas (AKA Hydrangea paniculata), Steve's suggestion. My favorite is 'Quick Fire' since I like that the flowers start about weeks earlier than other varieties of panicled hydrangeas like 'Limelight' and have more rounded and open flower clusters than most other types. They also turn a gorgeous bright pinky red in fall after much of the summer being white. Just a personal preference - any of the Hydrangea paniculata would be lovely. Another option would be rugosa roses (AKA Rosa rugosa), the classic beach rose which is quite salt tolerant. They come in various shades of almost red, pink, and white, and can be either single and double flowers. Rugosas do have some wicked thorns, so if that would be a problem, you'd want to avoid them, but there are some less thorny but still low care roses. You could even do a combination of roses and hydrangeas if you wanted, perhaps clusters of three of each along the length of the property line.

I agree with mulch the heck out of them. But I'm wondering what the root systems look like. Have you dug up any of the dead ones to take a look at the roots? That veinal yellowing reminds me of a girdling problem. You might want to check for girdling roots. Container grown plants can often suffer from that. Where did you get the plants from? If the plan was for a formal clipped hedge, I'd probably use Acacia longifolia instead. I think a more naturalistic hedge with Grevillea, Banksia, and Melaleuca would be more interesting though.

Replace the dead trees, 15 dead out of 65 planted is not great, but not the worst either. The soil may be too rich for conifers, try ordinary native soil for the replacement trees, don't disturb the other trees that have taken. Moreover, don't fertilize new transplants, it would have the undesired effect of stimulating the growth of foliage, whereas they should instead grow the roots they lost when they were dug up. Note that these large transplants have to continue their lives with as little as 5% of their roots. Good luck!