Spot on, #4 and #5. I have experience navigating through these issues. I used an attorney (based in Thailand) who had a lot of experience and I still spent a lot of time and effort on the process. There are exceptions to the rule, so you need to be well versed in the law. Ultimately we were successful (my wife has been in the US for six years now) but it took 18 months from start to finish. I also made four or five trips to Vietnam, including her interview (they questioned me). From the consulate the visa application goes to a special office in the DoS in Washington, where it will undergo additional review (a true black box). If you want the name of the attorney send me a DM and I'll provide.