FYI, this is an edited reply. My closing comments initially were not very diplomatic. Please accept my apology if they seemed insensitive.
Welcome back to the forum, but I'm sorry you found it necessary after the strong, reasoned, science-based reassurance you had from Dr. Hook. I have the impression you have a very inflated view of HIV risks. In the US and most industrialized countries, it remains quite rare as a heterosexually transmitted infection, except in special settings like commercial sex work, especially when combined with injection drug use. If you have HIV, you would be the first in my 14 years of answering online forum questions like this. And that isn't going to happen.
Directly to your questions:
1) Zero chance of transmission. In regular couples (e.g. spouses) in which one person has HIV, if the viral load is undetectable, transmission never occurs despite regular unprotected sex. Many such couples forego condoms entirely, especially if attempting to conceive.
2) I can't say "how much" virus is in pre-ejaculate. But even with semen deposited in the vagina, if the male is infected, the transmission risk for the female partner is about 1 in a thousand. So what can it possibly be with the far more trivial exposure to pre-ejaculate fluid that you are concerned about?
3) The status of your partner's other partner is irrelevant. What matters for you is HIS status, not hers. Given his negative test results, you really don't need testing at all. But if you do it, you are considered in a low risk category and a single antigen-antibody (duo) test 6 weeks after the exposure will be conclusive. There is no need to test at 12 weeks or any other time.
4) I have to suspect your partner is being put off by your insistence on this. He isn't obligated to show you his written test results, and I see no reason you shouldn't trust his statement that h isn't inected.
5) Zero risk. I've never heard of anyone catching HIV from such an exposure. See above about 1 in 1,000 for ejaculation in the vagina.
6) The main ARS symptoms are sore throat, fever, inflamed/enlarged lymph glands especailly around the neck, armpits, and groin, and often a non-itchy body wide skin rash. Onset is almost always 1-2 weeks after exposure. Since you're now beyond 2 weeks without symptoms, you needn't worry further about this aspect.
So do your best to not worry about this. If you were my own patient or someone close to me, such as my daughter, I would have recommended against even being tested for HIV -- the risk was zero for all practical purposes. That said, like many in such situations, testing may be worthwhile because you may gain more reassurance than from Dr. Hook's or my advice. But please also note that repeated questions about the same exposure or risks are not permitted. Let me know if anything isn't clear, and perhaps save any final comments until after you have been tested.
Best wishes and stay safe, as you have been doing!