I ended up just using that Google Map for the 10K. I exported the KMZ file and converted it to GPX. Here is what it looks like in Strava (28ft of elevation gain):
View attachment 711639
I did my best to build the half map and the mile markers are close. Here is what I got (12 ft elevation gain):
View attachment 711640
In Strava there seemed to be a public heat map that corresponded to most of the course and since much of this isn't re-use as far as I can tell I'm guessing whomever ran/biked the course for measurement uploaded to Strava.