So, I have been doing some modelling recently, and I have a pretty shitty computer. I occasionally had a problem where it would freeze up, but then it would unfreeze quickly, and it didn't happen often. Now, it freezes all the time, and takes about 10 minutes to unfreeze, and then freezes again quickly. It doesn't go grey for noot responding, but it says not responding in Task Manager. Here is the project file so far, if it helps.
I would guess that the slowdowns are related to the Booleans, which are quite processor-intensive. First thing I would do is turn off the Boolean object in your backups null. Just turning off visibility doesn't keep it from calculating. Then, unless you need the Boolean to remain editable for some reason, convert it to geometry with the "make editable" command. To speed things up further, select all the resulting parts and run the "connect and delete" command.