I don't think much is lost. The Ada Initiative is mostly involved in sensitivity education. This is important, of course, but there are a lot of organizations that do the same thing.
I think that there are other organizations that are more effective for your charity dollar. This includes Outreachy, whose success can be measured.
I really like it. Unfortunately, it is not clear what license ETBembo carries, if any. In fact Tufte indicated that ETBembo is not public. So it may not be legal to use it. I think that Dejavu serif is an acceptable (superior?) substitution.
If by "stringing him along" you mean declined every single advance made by him.
"No thanks" should be more than enough.