Only members of the Board, since paragraph 1 requires the election to be made from amongst them. Under Article 68(3) the Board is composed of the head of one supervisory authority of each Member State and of the European Data Protection Supervisor, or their respective representatives, so the Chair will always come from that circle.

A simple majority of the Board's members, which mirrors the general voting rule in Article 72(1). The Regulation reserves a two-thirds majority for other matters, such as dispute-resolution decisions under Article 65(2) and the adoption of the rules of procedure under Article 72(2).

Yes, but only once more. Paragraph 2 makes the five-year term of the Chair and the deputy chairs renewable a single time, so continuous service in the same office cannot exceed ten years.

Article 73 is confined to the election and the term of office. The Chair's tasks are listed in Article 74(1) and include convening the Board's meetings, notifying decisions adopted under Article 65 and ensuring the timely performance of the Board's tasks, and under Article 75(2) the secretariat works exclusively under the Chair's instructions.