FWIW, I've had issues with long saves etc in the past, not so much now with v.10
I'm running TCMP10 on a 27" iMac (custom model with 32Gb RAM & 3 Tb HD) as well as on my 15" MacBook Pro (mid-2014 with 16Gb RAM 500Gb HD) - I've never been able to see any practical speed difference whatsoever between the two computers and also have long been wondering if the program actually uses all the processor cores to the max. Doesn't seem like it to me, but what do I know about such things...
I have "Menu meters" installed with shows the core activity, it rarely if ever does it show the program using more than 20-25% of the core processing capacity, even when saving or rendering very large files...
(The real bonus with the iMac is the amazing 27" retina screen which makes it possible to see so much more of the drawing compared to the MBP).
Be that as it may, Tim O gave some good advise some time ago that seem to have helped me in the speed department.
In TC Preferences>Filing... uncheck "Save compact files" - this had a big impact on my saving speed.
oops, just noticed your screenshot shows you don't have this checked, so never mind...
But you do have "Save Preview image" checked - try unchecking it, might help...
BTW, since day one (and v8) I've checked "Clear undo on save" - not related to speed but I don't understand why one would want to keep undone items after saving...
And, I very soon disabled AutoSave as it drove me nuts interrupting my work.
Finally, I notice one of your screenshots have what appears to be a corrugated roof.
My current project is quite a complex piece of equipment (file size 576 Mb) which has a relatively small object of "expanded metal" i.e. metal grating. The object is kinda similar is shape as your corrugated roof, with lots of curves etc. The big drawing usually presents no problems, but when the layer with the expanded metal object is active (i.e. when it's visible) it radically slows down screen redraw, saving and other activities.
You may want to try to put that corrugated panel (and similar objects) on separate layers and then not show that layer - just a hunch, but it may help in speeding up your saves.
Finally finally, make sure you're not running any other programs at the same time.
Check in System Preferences...>Users & groups... > "Log in items" that nothing else starts up automatically on reboot. Make sure not other users are logged in! Run Disc Doctor, rebuild disk permissions, restart, run nothing else and see if that does not improve things for you.
If none of this, or mitch's advise, works you need to get in touch with dtaylor and/or tech support to get this resolved. They'll need a copy of your file, so put it on dropbox (or similar service) and provide the link, as you can't upload big stuff here.