HappilyRetired: You said that some poskim allow attending a bar mitzvah in a Conservative house of worship. Who, specifically? I have never heard of this–as far as I was aware, attending any religious event in the sanctuary of a Conservative place would be asur according to all Orthodox opinions.
I don’t think it matters if it’s one of those few Conservative places left that still has a mechitza. The C movement doesn’t believe that the Torah (particularly Oral Torah) is from Sinai.