So looking at your model, I see a few things but all are easily fixed.
First, you’ve selected an architectural template which affects the units. For this sort of project it would make sense to use Fractional units, set Precision high and disable Length Snapping.
Second, you’ve modeled this as if it was going to be whittled out of a large block. It would make your modeling easier if you draw one part that you make in the shop and make it a component before going on. Here in the foreground I’ve started to redraw your planer table using components. I moved them away from each other to illustrate that they are separate pieces.
You have some unusual dimensions in your project that probably need some correcting. You have the bottom of the case at 7/16 in. thick and the top at 7/8 in. thick while the left case side is a bit shy of 15/32" and the right side is just shy of 7/16 in. thick.
As I said, all of these things can be rectified.
Here I’ve taken the liberty of making all the parts 3/4 in. thick and used components (copied as appropriate). I set units to decimal to show the components are accurately modeled.
SketchUp obviously isn’t Fusion 360 so you will need to learn different methods. Not sure why you can’t open it once you saved it. Do you get a message when you try?
What version of SketchUp are you really using? Your profile is contradictory. It says you are using SketchUp Free which is a web based version but it also says you are using SketchUp 2018 which is a pro desktop client version.