> How much evidence needs to be compiled to show a relationship, one
> language to another.
It is regular patterns of relationship, rather than quantity of similar
words, that linguists look for. But there are a number of actual cases
where opinions differ from linguist to linguist, and change back and forth
with time and swings of fashion, so it isn't a clear cut process. In the
case of Hittite, it was the recognition of a highly unusual paradigm
in -r/-n- that finally proved its connection to IE.
Peter