Welcome to the forum. Thanks for your questions. I'll go directly to them.
1) There are no official moderators or experts on MedHelp's HIV community form. Everyone participates because of their personal interest in the topic. Many of the regulars are very knowledgeable and usually have excellent advice. I believe some are or have been HIV prevention counselors, but most are not medical professionals and it is appropriate that they stick to official advice about HIV testing. CDC and many other agencies do not consider negative tests to be conclusive until an antibody test has been done at 3+ months after the last possile exposure. In contrast, Dr. Hook and I are experts in this area, and we have the freedom to give advice based on the best science.
Below I have provided links to other threads that go into these issues in more detail.
2-4) Negative 4th generation ("duo" or "combi") tests are conclusive any time 4 weeks or more after the last exposure. There is no second window period; that's an urban myth (see the third thread linked below, in particular the follow-up comments December 25). Your negative result at 5 weeks proves without doubt you do not have HIV and you do not need further testing. You can safely have sex with your partner. However, if you would like the additional reassurance of a negative result at the official interval, feel free to have another test at 3 months. Personally, I wouldn't do it and I don't recommend this to my own patients.
http://www.medhelp.org/posts/show/1855891
http://www.medhelp.org/posts/show/1891685
http://www.medhelp.org/posts/show/2064508
I hope these comments have helped clear up your confusion on these issues. Best wishes and stay safe--
HHH, MD