That's one of the downsides of being in a rarer haplogroup. I have plenty of mtDNA matches (K2b), but hardly any Y-DNA matches for the same reason (N1c1).
If your FGS results are in, and it shows no matches, then you don't have any exact FGS matches. The caveat about possible medical implications is only for sharing with project administrators. There are separate checkboxes on the User Preferences for each project you're a member of, whether to allow the administrator to see your full results.
1. Possibly, since anyone can upload mtDNA results to MitoSearch who's tested at other companies too. However, some people leave the default setting on FTDNA for "Please choose your preference for matching purposes:" to "I want to restrict the display of matches only to my Surname Project." If so, they won't show up as your match unless you're both members of the same project, and you have that project currently selected. For that reason, it's advantageous to join as many applicable projects as possible--for your haplogroup, ancestral locations, etc.
2. I wouldn't contact any HVR2 matches unless the surname of their ancestor is in your direct maternal line. Even a perfect match at HVR1+2 could mean a common ancestor more than 1000 years ago.
3. The high resolution matches are exact matches on HVR1+2, and low resolution just on HVR1.
4. Maybe your HVR2 match didn't list a location for their maternal ancestor? I don't find the Ancestral Origins to be particularly helpful. There's a more comprehensive chart of maternal haplogroups in Europe on the following website:http://www.eupedia.com/europe/european_mtdna_haplogroups_fre...