Report. I had the project imported for about a second. All scenes except one open normally. "FreakShow_RingMaster.tscn" does not open. It is corrupted.
How well Godot handles huge files is an interesting question and I will investigate it.
General thoughts. I will be lynched for them here, of course. Very large projects are very costly to develop. In the sense that, among other things, they require investing in hardware that can run them normally. A total volume of several gigabytes and a lot of small files is almost a server load and needs to be respected accordingly.
That's what I opened your project in:

…and two 2Tb disks.
I envision very slowly expanding the project. Trying on more modest games to earn money for equipment that can handle larger amounts of content and space. If such games will not be in demand, it is clear that all plans will remain in dreams.