1. Is the Seventh-day Adventist Church (SDA) a cult?

No, although as this is such a subjective question, it really depends who is asking. Many Atheists, Agnostics and non-Christians would no doubt label all of Christianity a cult. The Jewish leaders seemed to think of the Early Church in these terms (Acts 5:33-39).

See: http://en.wikipedia.org/wiki/Criticism_of_Christianity

The most ‘official’ and authoritative position amongst Evangelical Christians is from Walter Martin, founder of the Christian Research Institute (CRI), and author of Kingdom of Cults (1965). The position CRI is that Seventh-day Adventist (‘SDA’ or ‘Adventist’) theology is essentially ‘orthodox’:

“It now appeared that the structure of SDA theology was essentially orthodox. Adventism affirmed the inspiration of Scripture, the Christian doctrine of the Trinity, and Christ's deity, virgin birth, vicarious atonement, bodily resurrection, and second advent. Martin, who had written extensively on the subject of American-based cults, immediately recognized that this was not the doctrinal statement of a typical cult. He began to believe that SDA, at least as these men represented it, had been very misunderstood by evangelical Christianity.”

See: http://www.iclnet.org/pub/resources/text/cri/cri-jrnl/web/crj0005b.html”

And: http://www.equip.org/articles/seventh-day-adventism

“Martin’s conviction remains my own—that one cannot be a true Jehovah’s Witness, Mormon, or Christian Scientist and be a practicing Christian in the biblical sense of the word. Those sects proclaim a different God, a different Christ, and a different gospel (2 Cor. 11:4; Gal. 1:6-9). But it is possible to be a Seventh-day Adventist and a true follower of Jesus Christ despite certain distinctive Adventist doctrines that most evangelical Protestants respectfully consider to be unbiblical.”

See: http://qod.andrews.edu/docs/08_kenneth_samples.pdf

The view even taken by Roman Catholics, who have no reason to show bias to one Protestant Church over another, also states:

“Seventh-Day Adventists agree with many Catholic doctrines, including the Trinity, Christ’s divinity, the virgin birth, the atonement, a physical resurrection of the dead, and Christ’s Second Coming. They use a valid form of baptism. They believe in original sin and reject the Evangelical teaching that one can never lose one’s salvation no matter what one does (i.e., they correctly reject "once saved, always saved").

…Adventists also subscribe to the two Protestant shibboleths, sola scriptura (the Bible is the sole rule of faith) and sola fide (justification is by faith alone). Other Protestants, especially conservative Evangelicals and Fundamentalists, often attack Adventists on these points, claiming they do not really hold them, which is often used as "proof" that they are "a cult." However, along the spectrum of Protestantism (from high-church Lutherans and Anglicans to low-church Pentecostals and Baptists), there is little agreement about the meaning of these two phrases or about the doctrines they are supposed to represent.”

See: http://www.catholic.com/library/Seventh_Day_Adventism.asp

For a full examination of extremist SDA offshoots, including the Branch Dividians, Creationist SDA Church and Seventh-day Adventist Reform Movement, please visit the site 'Sevy Taliban':

See: http://sevytaliban.blogspot.com.au/