What are character traits of Antonio evinced in Act I, Scenes 1 and 3 of The Merchant of Venice?

In The Merchant of Venice, Antonio exhibits the characteristics of melancholia, intelligence, and confidence. In addition, he has the qualities of generosity, loyalty, and love.
In Act I the first scene opens with Antonio in a dark, brooding mood for which he himself has no explanation, and for which there is no explication in the play itself, unless it is used as foreshadowing. When Antonio cannot define his melancholy to Salerio, his friend gives him a short lecture and then departs.Later, Antonio's cousin Bassanio enters and tells him of his wish to woo Portia, a wealthy heiress who lives in Belmont. Bassanio explains that he needs three thousand ducats. Although Antonio has his money invested in his three merchant ships, he generously and lovingly offers to help his friend Bassanio:

My purse, my person, my extremest meansLie all unlocked to your occasions. (1.1.138-139) 

Since all his "fortunes are at sea," in a gesture of true friendship, Antonio instructs Bassanio to go and learn what he can obtain with Antonio's good credit from one of the moneylenders in Venice. Later, when Bassanio returns to Antonio, he tells him that Shylock has considered the loan. So, Antonio talks with Shylock, who quickly reminds Antonio of his insults upon Shylock's usury; further, he mocks Antonio with this opportunity to do so. But, Antonio merely replies that he will most likely insult Shylock again. He makes no apologies, as he is

        ...like to call thee so [a dog] again,To spet on thee again, to spurn thee too (1.3.127-128)

Instead, Antonio curtly tells Shylock to lay down the conditions of the loan. Shylock says he will charge no interest, but will demand a pound of flesh if Antonio cannot repay the loan in time. Bassanio worries, but Antonio confidently informs his friend that there will be no problem:

Bassanio. I like not fair terms and a villain's mind.Antonio.   My ships come home a month before the day. (1.3.176-177)