First welcome to the forum. I think it is great that you are sharing your experiences as a female about a partner who is doing PE and that you actively support him. Quite brave.
I would like to ask a couple of questions. It may be too much, so if you are not comfortable answering I will understand.
You said you actively follow is progress, which is cool. How much size gain has rootsnatty gained since you started seeing him, length and girth? Also how much time (weeks, months, years) does this cover? Do you measuring for him or just watch him do it?
You said that you can take almost all of his length, 9.125 inches PBEL. How much length do you take and how much is still left outside of you do you estimate?
It sounds like he is hanging. What are you thinking about his PE activities when you are spending time together and he is hanging?
Again, welcome and thank you,