1 - SR is like the distinction between soul and body; we know it's true but we can't explain any of it. If you've been on longer semen retention streaks you'll notice esoteric events like a teacher giving you an answer during the middle of an exam (this happened to me last night) or a girls gravitating towards you everywhere you go (also happened to me yesterday and today). Much of the effects of SR (sheen on skin, glowing eyes, better body posture, lower inhibitions) can be explained through a lack of prolactin in the body and excess minerals from not ejaculation. However, there is a element of semen retention, usually called an aura that we can't, and likely will never be able to explain.
2 - Lifting weights is the best way to transmute sexual energy. Studying, cold approach, and writing are close behind lifting. Everyone has time to go to the gym. If you say otherwise you're lying to yourself.
3 - If you're not in a relationship don't worry about karezza and just go straight celibacy. Ejaculation via casual sex once every 2-4 weeks (longer separation if you're in your 40's and 50's) is fine. Most girls these days aren't relationship material anyway so don't think you have to find wife material to have sex.
4 - It's not a negative aura. I've recovered plenty of negative attention from other males it's likely because my aura and body language are so strong they feel threatened by it. You're going to polarize other males on SR; they're either going to be very submissive or very defiant (think a beta male challenging the alpha on an animal documentary).
5 - Flatline is a symtom exclusive to porn withdrawals. I went though 6 months of flatline and another year of waves of withdrawals before I only experienced benefits from semen retention and low artificial dopamine. If you're in your 20's and grew up on internet porn your brain is completely fucked and it will usually take a year minimum to reach your natural dopamine state again. It's a long journey to reach homeostasis.
6 - I started flapping when I was 13 and quit when I was 21 (24 now). It was too long ago for me to be able to answer this.