For point #1, "Does sex lower testosterone?"
For that I point to this article on Examine.com. which is far more cited and scientific than that Tiger Fitness article. It does note that men who are abstinent for three weeks see a slight increase in overall testosterone levels. It does not seem to effect the amount of testosterone that's in the blood. The overall summary states:
Ejaculation results in changes in prolactin (increase) and dopamine
(temporary decrease), but does not result in changes in testosterone.
Although prolactin and dopamine are both involved with testosterone,
they do not appear to influence testosterone levels acutely.
On top of this, there is a very lengthy stackexchange question that already covers this topic in far more detail. Oddly the top answer points to a lot of the same studies that are in the Examine article, but it comes to a overall different conclusion.
What's missing is just how much all this effects performance. There are no studies as far as I know that show a performance comparison between sexually active and abstinent men. We know that more testosterone typically means better recovery and performance (that's why steroids work). Overall though I do not think it would have that much of an effect on the average person.
For #2: No. People do HIIT and still make massive gains. In fact, people do HIIT because it's better for keeping gains.
#3 & #4: Please... Even the most intense session isn't going to put a dent in glycogen. And if there really is an energy problem, them maybe you could spare to do some cardio.
#5: You could say this about literally everything that's not exercising. You'll make progress as long as you stay committed and consistent with training.