Thanks for bringing up this thread, 5fish. The discussion is from long ago and far away but I'm game to revive it!
Most of what you've posted is accurate - Forrest did die poor. After the war, Brownlow saw to it that Forrest had to pay fines, fees, penalties and exorbitant taxes on returned properties. He also had to pay many legal fees based on warrants and other charges stemming from the war. All this was supposed to be forgiven and a clean slate given by the terms of his surrender and parole - but Tennessee's governor had it in for this most famous rebel. These costs were designed to be heavy enough and often enough to break his bank roll. He had, after the war, partnered with several Union soldiers to try to rebuild the one plantation he had left - Green Grove. Because of a lack of cheap labor and the various financial problems, Forrest was not able to rebuild the plantation, which went to his partners. He retained the saw mill on Sunflower Landing. There was also a heavy problem when Forrest vouched for a friend's big loan and the friend defaulted. At that time he was about as penniless as he ever got - he and his wife had a ten dollar bill lying on the table between them, and thousands due the bank the next day. Forrest said, "Will you let me hunt up a game of draw?" She said, "Gambling is a sin. No good comes of sin." He replied, "It is a matter of honor." She said, "Then I will be here praying." She then sat down in a chair in front of the fire with her Bible. So, Forrest picked up the bill and left. He won enough money to pay the loan and, as he was putting the money in his hat to leave, the other gamblers pleaded with him to stay and give them a shot at getting their money back. "No, gentlemen. I have played my last game. My wife is sitting at home with her Bible in her lap praying for me." He then left - and never gambled again.
Except for the railroads. That seemed to be a game every ex-general tried! Forrest, having been a master at ripping them up also made a lot of observations about what could be done to improve them, and wished to put some of these innovations into play with the new railroads. He sold a large number of bonds to various towns, who reneged on the payments, and the most he sold was to the city of Memphis. They dissolved themselves as a city to get out of paying back the bonds - and that act pushed Forrest into bankruptcy. It also almost resulted in a duel - one of the aldermen was Minor Meriwether, a former staff member of his, and who came up with the dissolve the city scheme. He told Forrest, who told him if he did that at the council meeting, "One of us will not leave there alive." That created a huge hullabaloo - anybody else might be blowing off steam but if Forrest said he was going to kill you, there was very apt to be a death in your family! At any rate, this dire extreme was avoided and the city went ahead with its plan to shaft Forrest on the bonds.
As a last ditch effort to make a living and for the health of his wife, he moved to President's Island off Memphis, which was then completely undeveloped. He planned to see if corn would grow there. He contracted with the prison system to have prisoners come live on the island in barracks. He was not a warden or prison guard but one of many who contracted for cheap labor. O O Howard was in charge of this program and reported that Forrest's accommodations on President's Island were very good, no complaints by his laborers. The dog trot cabin from his old plantation was set up for their main house but it caught fire and burned down with everything in it. Many very important papers and family memorabilia was lost. Forrest was ill by then and went to live with his brother Jesse. He died at Jesse's house.
One note - Forrest did not have to die poor. Mary Ann, his wife, had a goodly amount of money of her own - she had inherited a lot from both the Montgomery and Cowan sides of her family. Her husband absolutely refused to touch her money, not a dime of it, even though it likely would have pulled him through several financial difficulties. He simply determined she keep her money in the bank - he knew she would outlive him and would need the money herself. After his death she went to live with her son Willie. He was a widower whose wife had died after giving birth to their third child - Mary Ann took over raising his kids.