Let me address a couple of your questions:
Regarding measuring venous leak: that can be accomplished with a penile ultrasound at a urologist's office. On my post I put "venous leak" in quotes since I have not had the test and have not been formally diagnosed with that condition. However, I certain suffered from the primary symptom: losing an erection quickly. That has been greatly improved. If you look on the main Peak T web page, one of the primary causes of this condition is LOW T. When the cells at the base of the penis are starved of T, they can weaken/wither causing the mechanism that traps blood in the penis to malfunction. There are other causes of course: hardening of the artery walls etc.
You should experiment with various NO boosting supplements including the ones you mention. It will vary by person, but they can greatly boost the effectiveness of Cialis/Viagra. Of course strong T levels do that as well, since T/E regulates the NO production in the penis to a great extent.
Here are some other tips from the Website:https://www.peaktestosterone.com/Increase_Nitric_Oxide_Naturally.aspx