I don't want to fix him. I want him to tell me what is wrong with me, with him and/or with us that makes things this way. Then we can evaluate together what is fixable and what isn't.
What has he said so far? Any clues about why the low frequency? I'm very curious about this.
Don't assume there is a problem with you, from what you have said it doesn't sound like it. You are on the right track with the process though, this is more or less what did and it helped me at least understand things. IMO knowing the fixable and unfixable is critical. You may not be able to get him to discuss it much more than just stating some elliptical reasons why doesn't feel like it, you may have to put the puzzle together yourself.
I found that being direct was the least productive approach, I had to bring it up in a way that didn't make it seem that my W was s*xually deficient. It was as if I had to mention it, then it would ferment and she would bring it up at some later date and expound on it then. No real time discussions, I think she is very uncomfortable talking about it and needs to sort it out before responding.