Just so we're clear here, you want Fiddler to intercept ALL HTTPS connection requests and pretend like they succeeded? And then you want to redirect every other request to a fixed URL? This is a pretty odd configuration, I'm not sure why you'd want to do that.
It's not clear what you mean when you say "plenty of requests"-- you should be able to make at least several dozen requests in parallel (on a very low-end machine) and hundreds of requests in parallel on a faster machine.
Timeouts are controlled by preferences and they default to more than one minute.
Which version of FiddlerCore are you using? What flags did you pass to your Startup method? Did you adjust the threadpool growth algorithm as demo'd in the Program.cs file, or are you using a modern version of FiddlerCore with the FiddlerCoreStartupFlags.OptimizeThreadPool flag set?
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