My Mother’s family came from an island in the inner Hebrides called Colonsay. I once looked on their web site and noticed there are several Gaelic speakers on the island.
I would guess the Western Islands have the most Gaelic speaker in Scotland and probably by a long way. I have also read that the Western Islands are last bastion of devout Christians.
Here's hoping that events such as the annual Hebridean Celtic Festival, which began in the 1990's, will help to keep their traditions alive.