What is the information on chapters 18–20 and others in The Westing Game?

In chapter 18 of The Westing Game, Turtle and Flora grow closer, and Turtle begins addressing Flora by the nickname "Baba." At Turtle's insistence, they unload all other stock and put their money into Westing Paper Products, which begins to climb in value. Sandy compiles information on Baumbach, Amber, Deere, and Pulaski to share with Judge Ford. Theo instructs Doug to follow Otis Amber, and Doug jogs all over town to keep track of him. Angela quietly reveals that she doesn't want plastic surgery to fix her cheek, and Turtle instructs her not to talk to anyone about the bomb. Dr. Deere brings Chris to the hospital to see a neurologist about his condition.
Chapter 19, encompassing all of Thursday, begins with Turtle and Flora anxiously monitoring their stock. Otis suggests to Crow that James Hoo is the bomber, and she is suspicious of Hoo until he gives her insoles of his own invention that relieve her aching feet, proving to her that he is good and could not be the bomber. Sandy and the judge review his notes on Crow and the Wexler family and realize that Sydelle Pulaski was mistakenly included in the list of heirs. Chris finds an envelope containing clues (WITH and MAJESTIES) in his bathrobe and delivers it to Angela as a gift from Theo; the words were actually put there by Crow, unbeknownst to Theo.
In chapter 20, Turtle instructs Flora to sell all the stock after Westing Paper Products reaches its highest peak in fifteen years. Doug follows Otis around but can't find Theo, and his feet find relief thanks to the insoles his father invented. Following a hunch regarding their last clue, Theo experiments with fertilizer in the chemistry lab at school and causes an explosion, which makes the bomb squad suspicious of him. Sandy completes his notes on the Theodorakis family after Judge Ford questions George Theodorakis, who once had a romantic relationship with Violet Westing. Sandy and the judge conclude that the former wife of Sam Westing must be one of the heirs and that her life is in danger, since she is likely the person he would most want to punish.
For more information on The Westing Game, including detailed chapter summaries for the entire book, see the link below.