Very impressive!
I notice you went for the larger denser resource patches.

Currently playing with the default settings myself, as well as having to worry about being attacked.

The graphic I'd like to see improved the most is the resources/terrain/hills* set. To me the hills are very jarring, hard to tell apart from mineral resources, and the gray clashes with the gray of most of the factory machines.
And here I had been thinking the hills might be wasteland terrain ...

While playing in free play mode I am experiencing that the game periodically slows down to a crawl, from the normal 120 fps to around 3 fps, also most notably, during this slowdown, the GameUpdate usage in the F5 screen shows GameUpdate taking about 100% of usage load and showing up to about 300k mc ...

Nice pictures!

My savegame is probably less impressive at only 33.8 MB after about 28 hours playing in game time, so about half that in real time.
But since I have spent most of the time building rather than exploring, I suppose there could be something impressive there too.
Especially proud of my ...

I have been having this issue too, mostly when setting filters in inserters, but the other situations listed make sense too.
Randomly lost quite a few buildings to this before figuring out what was happening.

My save names can no longer contain spaces or numbers.

I have this problem too.
The first time I ran the game it worked fine until closed.
Every time after that, it runs at my monitor refresh rate at 120 fps, which I guess makes the game run at double speed.
This makes it harder to do everything, though still possible.