After five attempts, I was finally successful in getting my Windows 10 Spring 1803 Update to work, so I wanted to explain how I finally did it, in case anybody else encountered similar problems.
I initially tried using the regular Windows Update method to automatically download and install the 1803 update. However, that method failed at least two times (towards the end of the install process) and gave an error code of 0x8007001f.
I then tried using the Windows 10 Upgrade Assistant, but that also failed towards the end, and simply reverted back to my earlier Windows installation.
Next, I downloaded and ran the Media Creation Tool. The first time I did this, it displayed an error message part way through saying that HitmanPro.Alert had blocked a file operation, and then it also eventually failed to install, again reverting back to my earlier Windows 10 installation. This time the error message was 0x80070402b - 0x4000D "The installation failed in the Second Boot phase with an error during migrate data operation".
Finally, after doing some online googling for possible fixes, I came up with a package of potential solutions and tried them all at once. I did this instead of trying them one at a time because the installation process had been taking about 2-1/2 hours each time before failing, and I wanted to avoid sitting through many more lengthy attempts.
Here are the things I did to finally get the 1803 update to install on my computer:
1. Using Revo Uninstaller, i uninstalled the following programs:
HitmanPro.Alert v18.104.22.168, Hellblazer Maps Pack v7.2 (a mod for Civilization 6), All of my Creative Soundblaster related programs (Creative Alchemy, Creative Audio Control Panel, Creative media Source 5, Creative Software Autoupdate, Creative Soundblaster Properties x64 Edition, and Creative Wavestudio 7)
2. Manually deleted the folder containing the MalwareBytes Antirootkit program.
3. Using Msconfig, set my system to clean boot as follows: Opened msconfig, navigated to the services tab, selected "Hide all Microsoft Services", clicked on the "disable all" button, then clicked "Apply" and "OK".
4. Opened Task Manager, went to the Startup tab, and disabled most of the programs listed there.
5. Restarted my computer, and then in Administrator mode successfully ran the Media Creation Tool 1803.
6. After about 2-1/2 hours, Windows Update 1803 finally successfully installed! Hooray! Hooray!
7. Windows then automatically reinstalled some Creative Soundblaster files.
8. Using Msconfig, changed the settings to normal startup and restarted my computer.
9. In Task Manager, at the Startup tab, re-enabled all programs, and then restarted my computer one final time.
10. As a final wrap up, I then reinstalled one program that the Windows 1803 update had removed, the "Windows 7 Games for Windows 10 and 8".
Best wishes to all.