Looks great!
There's no good way to mount those hinges in a different place. Although there's a good chance there are no refrigerator lines in the area right above the old hinge mounting holes, you'd never know for sure, and it would likely need some reinforcement too.
It is possible to (epoxy) cement 2 reinforcement strips (2-3" wide, 6-8" long, 1/8-1/4" thick) on the outside then mount the hinges to those with very short, threaded, flat ended bolts that only go into the strips and don't penetrate the outer freezer shell at all.
How about simply lying the lid on top of the collar, using no hinges at all? Mount a few pins or wooden blocks for registration, so it stays in place.
I am wondering, in your build, how is the freezer cooling itself? The outer shell is the heat sink.