Just gonna ask a question. You mentioned that for years your wife has not felt popping was important to her In your post you also stated that she has told you for years that this time was just for you ect.
You then state

Recently, I've had some problems finishing the act, or popping.

Curious to what changed?
If for years you have been able to pop even though she stated the sex was just for your benifit (which I see as very loving and wanting you to be happy). Why all of a sudden does the burden of you not being able to pop fall on her shoulders? Her behavior did not change and from the above statement you said recently not always so this behavior did not always inhibit you from popping. So what changed for you?
Again just a question.