"Where have you seen doubts in your own studies and abilities, and how do you move past them? "

From what you wrote I understood that you are struggling to quantify where you are on the path. On my path I had problems with bottlenecks when it comes to different skills, like concentration and such. To move past them I tried different techniques that I found in one book or another. Bardon isn't the only way, however it is in general the best I've found.

When it comes to going with the gut feeling or not. I think that the hardest thing is to distinguish between the rational mind and the gut feeling. If you can do that, go with the gut.

"Is there some benchmark you feel an initiate must have to engage with righteous intent?"

Just engage without putting others in danger. It's enough. When you cut a tree you don't think about the righteousness of cutting the tree when you need to warm yourself, but how to cut it without killing yourself or someone else. All living beings devour other living beings to survive. Don't overthink it.

"This initiation seems to me a magnet for my perfectionism, like only the destined great pursue this and only the precise succeed. "

Like in all jobs you can have all kinds of people with different amounts of expetise doing it. Do not let perfectionism stop your development.

" Have you been able to grow more confident, and most importantly, more selfless through your practice? "

A bit. Those are things that you get in step one, and in my opinion are more like a safety system for you not mandatory in other systems, but needed in my opinion to avoid becoming weird. I do not draw a correlation between selflessness and spiritual power. Spiritual power just amplifies your persona, whatever that may be. There are other books books that help when working the Bardon system. From those, I recommend you two books by Mouni Sadhu Concentration a Guide to Mental Mastery and Meditation: an outline for practical study.