1) the large majority of people go to hell
See ch. 32 § "The Mystery of This Number" of Life Everlasting: A Theological Treatise on the Four Last Things: Death, Judgment, Heaven, Hell by Fr. Réginald Garrigou-Lagrange, O.P. For example, he writes:
The number of the elect is known only by God. "The Lord knoweth who are His." [II Tim. 2:19.] …
Many Fathers and theologians incline to the smaller number of the elect, because it is said in Scripture: "Many are called, but few are chosen." [Matt. 20:16; 22:14.] Again: "Enter you in at the narrow gate; for wide is the gate and broad is the way that leadeth to destruction; and many there are who go in thereat; how narrow is the gate and strait is the way that leadeth to life and few there are that find it." [Ibid., 7:14.] Still, these texts are not absolutely demonstrative.
The common opinion of the Fathers and ancient theologians is without doubt that those who are saved do not represent the greater number. We may cite in favor of this view the following saints: Basil, John Chrysostom, Gregory Nazianzen, Hilary, Ambrose, Jerome, Augustine, Leo the Great, Bernard, Thomas Aquinas. Then, nearer to our own times: Molina, St. Robert Bellarmine, Suarez, Vasquez, Lessius, and St. Alphonsus. But they give this view as opinion, not as revealed truth, not as certain conclusion.
In the last century the contrary opinion, namely, of the greater number of the elect, was defended by Father Faber in England, by Monsignor Bougaud in France, by Father Castelein, S.J., in Belgium.
To conclude: some insist on the mercy of God, others on the justice of God. Neither one side nor the other gives us certitude. And the reasons of appropriateness which each invokes differ very much from the reasons of appropriateness invoked in favor of a dogma which is already certain by revelation, whereas here we are treating of a truth that is not certain.
2) hell is a place of fire and "physical" torment
Pope Benedict XII defined the following dogma in Benedictus Deus:
Moreover we define that according to the general disposition of God, the souls of those who die in actual mortal sin go down into hell immediately (mox) after death and there suffer the pain of hell.
The Council of Florence declared (DZ 693):
the souls of those who depart in actual mortal sin or in original sin only, descend immediately into hell but to undergo punishments of different kinds
3) that torment lasts forever with no hope of salvation.
St. Matthew 25:41, the Athanasian Creed, and Pope Eugene IV's bull Cantate Domino all mention eternal hellfire.
The Athanasian Creed (DZ 40) ends:
those who have done good, will go into life everlasting, but those who have done evil, into eternal fire. — This is the Catholic faith; unless every one believes this faithfully and firmly, he cannot be saved.