Yes, to both.
Gerry turned his back on her while he made the tea. “I know,” he said, “that you were responsible for my brother’s death.” While pouring the steaming water, he checked that the gun’s safety catch was off. “You were the only one close enough to do it.” He made sure the gun was covered by his shirt, and finished the tea. “Nobody else would have wanted him dead, except you.” He turned to face her, holding the tray. “And that, my dear, is why I asked you to come today.”
which doesn't work, because while there are two verbs in the dialogue, I don't feel that they are part of the framing sentence (if that makes sense).“I know that you were responsible for my brother’s death,” and while pouring the steaming water, he checked that the gun’s safety catch was off. “You were the only one close enough to do it.”
We are often told that the verb, said, is not very visible to the reader. Perhaps it isn't quite visible enough to take a following and.“—,” he said, “—,” and while pouring the steaming water, he checked that the gun’s safety catch was off. “You were the only one close enough to do it.”
He knew that Matt was responsible for his brother’s death, while pouring the steaming water, he checked that the gun’s safety catch was off. “You were the only one close enough to do it.”
He knew that Matt was responsible for his brother’s death while pouring the steaming water.