correct word and punctuation

To sincerely follow the guidance of our High Priest, who alone possesses the Law, which has been transmitted to the successive High Priests since True Buddha Nichiren Daishonin's advent and to comply with the traditional teachings.

1. Is 'alone' the correct word? What I'm trying to say is that our High Priest is the only person who possesses the Law.

2. Should there be a comma after "Law". I think it is necessary? Am I right?

3. Is 'advent' the correct word? What I'm trying to say is that the Law has been transmitted to the successive High Priests by True Buddha Nichiren Daishon first and then by the other succeeding priests.

Many thanks.