If it does open in 32-bit mode, you could save the project itself off to a new name in a new folder, which would keep the original.
I would then go through the process of stripping down the project to the midi tracks you wanted to keep, making notes of all plugins used and then remove them as well, so that you ended up with just the captured midi data.
Then that should be able to be opened in 64-bit X2a, plugins added back in, etc.
Just some thoughts - I don't know your particular needs, as far as retention goes, other than the earlier comment about largely wanting to preserve the midi.
I hope any of that helps, and in any case I hope you can get this to work.
Bob Bone