Upgrade to 4.5.2

Unfortunately I can’t find what the current version is. So, my issue is, I go in and do the Upgrade, the forward facing site everyone sees is fine, but if you try to use the WP-Admin area it is missing all the styles and scripts don’t seem to be working either.

Here are the steps I am going through to do the update.
1. Go to the Updates page in WordPress, click update to 4.5.2
2. Wait… and wait…
3. Finally a screen pops up that I need to upgrade my database, so I click the button to do so.
4. Wait, and wait… and wait, then…
5. Page goes to a “white screen of death”, upon returning the upgrade screen or the WP-admin page it literally is missing all the layout bits, so there is only text going down the page, but the front end of the site is unaffected.

Errors I am finding in the Chrome Dev console:
“Failed to load resource: the server responded with a status of 418 ()” — this is for a “load-style.php” file…

Then there is a JQMIGRATE: Migrate is installed, version 1.4.0

and one other error, it’s really just the same error again:
“Failed to load resource: the server responded with a status of 418 ()” — this is for a “load-style.php” file…

If I got to the front end of the site to check for errors, again, the page loads beautifully, the error says: JQMIGRATE: Migrate is installed, version 1.4.0
and a google maps API is missing, this is new, but I wouldn’t think that’d cause my backend issue?

What I know about the server:
It’s a managed server, it wasn’t “built for WordPress”, so they have been trying to “make it work” for wordpress since I installed, and I keep getting white screens when I attempt to delete plugins and I can’t authenticate anything. So, when I try to connect to my Google Analytics account, it just doesn’t work…

Is this possibly an issue with the database? maybe an old version of MySQL? Or is this an issue with a “Windows” server? Any suggestions would be great. I’ve literally been trying to update this site for a month now.

Thanks ahead of time.