Ah, I see what you mean. I'll give it a try.
If nothing else, I'll gain more screenshots to work with.
EDIT: Don't you hate it when you ignore the most simple solution to your problem?
I followed Seabody's advice, copied my backup and started playing it again to the point of lag, and it started to lag again, but not at the same point. Then I thought that maybe the problem was my active sim. Both times I got hit with lag, it was when my inventor was the active sim. Apparently the game isn't too keen on someone carrying around hundreds or thousands of pieces of scrap in their inventory. So I managed to move all her scrap to the workbench and my game runs so much better now.
So should I return to the later save and try moving her scrap to the workbench?