Issue from OP: displaying service beyond lowest cached level
This question/answer is found in a few different posts:
https://community.esri.com/thread/173082 (Ryan Kelso answer on March 10th 2017)
https://community.esri.com/thread/185761-tiled-image-in-arcgis-online-does-not-let-me-zoom-in-far (Kelly Gerrow answer on Nov 21, 2016)
To summarize the answers already provided in those links: You'll need to add a string to the properties on your ImageServer or MapServer resource that contains the cache using ArcGIS Server Admin Directory.
"resampling": "true" -> save your edits
TIP: For ArcGIS Server 10.3, I found that changing the "maxscale" property to the desired lowest scale (in addition to adding the resampling property) did not produce the desired effect of showing my cache below my lowest cached scale. Instead, I had to use ArcMap/Catalog Server Toolset --> Caching --> Manage Map Server Cache Scales --> select your service, then add the desired cache scales (e.g. 282.124294, 141.062147, 70.5310735) and ran the tool.
Running this tool creates additional scale levels for your cache, but does not create the actual tiles. However, we found these empty scale levels necessary to be able to use the "resampling" feature.
As an aside, I am curious why the "resampling" feature isn't be baked into the ArcGIS Server GUI or publishing workflow? Instead it seems to be a hidden extra, like a google Easter egg. Regardless, glad its even an option!
Issue from OP: Slow cache creation speeds
Esri best practices notes that creating a cache will go a lot faster if the data for the cache you are creating is local to the machine you are publishing to. By doing this, you are removing an unnecessary networking burden for the millions of requests that occur when publishing a cache. "If the data does not have to leave the machine, your tiles will draw more rapidly." I found this tip to be especially important and extremely helpful, and relatively easy to overlook for cache creation workflows. Caches that used to take 24 hours are taking just an hour or two at the most now.
Reference: Accelerating map cache creation—Documentation (10.3 and 10.3.1) | ArcGIS for Server