Short answers, pulled from the story.
Frémont earned the nickname The Pathfinder from his five western expeditions in the 1840s, during which he mapped the Oregon Trail, named Carson Pass and Pyramid Lake, disproved the myth of a "Buenaventura River," and co-authored widely distributed scientific reports that guided thousands of American emigrants westward.
During his 1845-1846 expedition, Frémont directed and participated in several massacres of indigenous peoples in California. The Sacramento River massacre killed somewhere between 120 and more than 700 Native Americans, depending on the witness account, with no expedition members reported killed or wounded. Kit Carson, who took part, later described it as "a perfect butchery."
Frémont was court-martialed in 1847-1848 after refusing to submit to General Stephen Kearny's authority in California following the Mexican-American War, believing he remained under the command of Commodore Robert Stockton instead. He was convicted on the 31st of January 1848 of disobedience toward a superior officer and military misconduct. President Polk commuted his sentence but gave only a partial pardon, and Frémont resigned his commission in protest.
On the morning of the 30th of August 1861, Frémont unilaterally placed Missouri under martial law and declared the slaves of all Confederate supporters immediately emancipated. Lincoln publicly revoked the emancipation clause on the 11th of September, fearing it would push neutral Kentucky and other border states toward the Confederacy. Frémont refused to voluntarily modify the edict, which ultimately contributed to Lincoln removing him from command on the 2nd of November 1861.
Yes. In 1856, Frémont became the first presidential nominee of the Republican Party, nominated at the party's June convention in Philadelphia. He ran under the slogan "Free Soil, Free Men, and Frémont," received 1,342,345 popular votes and 114 electoral votes, and lost to Democrat James Buchanan, who received 174 electoral votes.
Frémont appointed Ulysses S. Grant commander of the Cairo post at the end of August 1861, judging him an "unassuming character not given to self elation, of dogged persistence, of iron will" despite Grant's reputation as a drifter and drunkard. On the 27th of August 1861, Frémont gave Grant field command of the combined Union offensive targeting Memphis, Vicksburg, and New Orleans along the Mississippi River.