Welcome to the STD forum and thanks for your question.
Responding first to the question as worded in the title you chose for it: People who have HSV of either type (HSV-1 or HSV-2) are immune, or at least highly resistant, to a new infection with the same virus type, anywhere on the body. If both members of a couple have oral HSV-1, it is very unlikely that they will infect the other on the genitals.
Now looking at your specific questions:
1) As just noted, your doctor is exactly right.
2) Self infection of a new body site is called auto-inoculation. It is rare in herpes, except during the initial infection itself. For the same reason as above, people with oral herpes rarely transfer the infection to their own genitals.
3) Irrelevant; you don't have and are unlikely to ever get genital HSV-1. And if you had it, anybody who has ever had HSV-1 will not catch it from you.
4,6) Testing partners in this situation usually isn't necessary or recommended. The risk of transmission is very low when you aren't having an outbreak, although it isn't zero risk. But testing is an option if the partner is concerned and wants to know for sure whether s/he is already infected with HSV-1. Suppressive antiviral therapy has never been studied for its effect in preventing transmission of oral HSV-1 infection, and HSV-1 is less responsive to valacyclovir and the other drugs than HSV-2, so it is hard to predict how well this would work or what dose of drug to take. I don't really see a need.
5) You are right that doctors' understanding of herpes -- both HSV-1 and HSV-1 -- is highly variable. It's a complex issue. But the doctors who mostly reassured you are the ones with the more accurate viewpoint.
7) The symptoms themselves are pretty reliable. Among other things, every oral herpes recurrence is generally in pretty much the same spot every time (give or take half an inch). More widespread roughness/irritation of the lips probably is just chapping, not herpes.
8) To my knowledge, genital HSV-1 is no more common in women than men. But for the reasons above, if she is HSV-1-positive, she is indeed protected from re-catching it from you or anywhere else.
Here are 2 other threads that discuss genital herpes due to HSV-1:
http://www.medhelp.org/posts/STDs/Recently-diagnosed-with-Genital-Herpes-HSV1/show/969931 ;
http://www.medhelp.org/posts/STDs/HSV-1--devastated/show/1159077
Regards-- HHH, MD