Then get Squarespace to stop pinging random third parties on page load. The website owner is paying for Squarespace, why is it loading Google CDN (and Google trackers?)
And hosting a font file entails dumping it next to your index.html file and adding some very basic CSS. Not exactly difficult.
If you are a 60-year-old woodworker living in Appalachia trying to set up an online store to sell hand-carved flutes, this task is essentially impossible.
Caching was never mentioned as being a requirement. I'm only giving the most basic solution for achieving compliance with regards to hosting a font file.
Scope creeping, on a Sunday no less... where are we headed