I also have tried all of the Windows Update troubleshooting tips. No resolution. I was going to try the partition increase until I noticed that the needed partition size is 250 MB. I currently have 500+ MB. So, I see no need to be going through a disk partition exercise when I already have twice the amount indicated.
I hate to say it, as I usually give Microsoft the benefit of the doubt, but it looks like the download file must be corrupted. Will wait and give them the requisite two-week project time to locate and correct the issue.
Given that the security updates can't download, I figure maybe I will download the free security software that comes with my internet, and disable the Microsoft security until the problem is resolved.