Considering your strength, 10 reps in both squats and deadlifts with 2 times your body weight, I would find it amazing if you had low testosterone. My guess is your testosterone is at least high-normal. That would be a genetic blessing and I would not recommend putting that in jeopardy.
I would highly recommend blood tests before going forward. Your goals, leaning out and increasing endurance can be easily addressed through diet and training. IMO, you are seeking a short cut that has more “risk” potential than “reward” potential.
Give us some more feedback to clarify. The more you reveal the more questions I have.