FTE's
Jonas,
FTE is a specialist career - not just a job. Whilst echoing Genghis' comments above, I'll add my own view in support. I (not an FTE!) work with a group of FTE's who have been in the industry from between 5 and 25 years each. Please don't tell them I said so, but they are SMART, technical, professional folks.
All of them are enthusiastic about what they do, and all of them are also either Radio Model flyers or leisure pilots. I'm pretty sure all their formal education is at a minimum Aeronautical Engineering degrees - with a handful of MSc thrown in. Their depth of technical knowledge in aircraft and systems always amazes me.
They all enjoy coming to work and so I hope you get the hint that they're all pretty addicted to Flight Testing as a subject and as a career choice.
If you're determined, then please don't be put off. I recon there's enough guidance above to point you in the right direction. SFTE and RAeS definately a good place to start.
Good luck in whatever you choose.
Bear