I don't see any immediate issues that jump out to me. I wanted to make sure that you've reviewed a previous post where this exact situation was discussed as well:
Your steps appear pretty solid, so you may have reviewed it already, but one thing that was suggested in the previous post, and doesn't look like was confirmed, makes me wonder if it might be a clue to what's going on here as well:
Can you try to run the package with just one of the xcopy parameters defined?
If you delete three of the others, update the package, republish and try the install again I'm curious what the results are.
It may be that you want to set the program as a script instead so that you can handle it in package boot helper as one line instead of four: