OP thanks for making me search up this on Wikipedia. I guess this does answer the first question: premature ejaculation might indeed be the desired trait in most mammals…

I couldn’t find anything about length of intercourse vs reproduction rates… The only thing I could find that are remotely related are one suspicious blog post and this post by Mayo Clinic. It seems that the sources I could find (including one scientific article by WHO, wtf) suggust it is a serious issue for self-confidence/sexual well-being, but there doesen’t seem to be any documented fertility issues as long as it is PIV sex