I went ahead and signed up to answer my own question. Hallelujah, it works great! Minimum ping is around 51, and the spikes only go to 75 (those are probably something involving my line instead of Frontier's routing). End result: games are once again playable! I haven't tried Overwatch yet (I stopped playing it thanks to Frontier's terrible routing), but I expect to have the same experience there since I'm getting my traffic off their network and onto Outfox.
Feature request: Add option to connect to fastest Outfox server, not just fastest server. At the start of a game (and throughout the game) it will always think my own connection is the fastest. This is not the case no matter what the tool thinks, so I'd like to never use it. For Frontier, the speed is less important than the consistency and reliability.