1) Yea, sometimes the default stuff offered is a little lacking.
2) More angles are ok, but as a "director" you need to draw your players' attention to what you want them to focus on and constant camera spinning is usually not a good idea except for rare situations ;-)
3) Sure you can just grab some professional porn on different positions for ahem... research, they are more or less the same because there are certain "industry best practices" for a good reason i.e. most viewers like them.
4a) LOL HS2 packaged animations is like a compendium of "what not to do" case studies - almost everything is wrong there and I suspect it is this way because the original HS2 assets had issues around the female genitalia. As a result it doesn't depict animations like fingering, thrusting, pussy eating well so most of their animations tend to adopt angles that defocus these deficiencies.
4b) I think animations wise it's good enough. Some purists will argue for high fps, but to me time is usually better spent on other areas of the game. The only thing I would emphasize which I cannot see from the sample is the looping part, just make sure it joins as seamlessly as possible because jarring is one of the top complaints for poorly done animations.
5) I'm sure there's a solution somewhere, you might wanna contact some developers who use VAM and see whether there are any insights.
Cheers and take care.