What is the meaning of "Af b'Lev Olos Tif'alun"?
Rashi: Not only [did you not speak to prove that I do not seek to kill Sha'ul] - in your hearts you plot evil! "Olos" is like Avlos 1 , just like the plural of Shor is Shevarim, and the plural of Ir is Ayarim - "u'Sheloshim Ayarim Lahem" (Shoftim 10:4); it is an expression of a city.
Radak: "Af" teaches that even though the heart governs thoughts, and does not act, you make it an active party. I.e. you constantly think in your hearts evil so much, that it is as if it does it.
Radak citing Shocher Tov: David told them, the heart was created only for Emes - "v'Dover Emes bi'Lvavo" (15:2). You are unlike this!
Malbim: Refer to 28:2:2:3.
Radak: This is like "Lo Sa'asu Avel" (Vayikra 19:15), just here the Vov is silent.
What is the meaning of "ba'Aretz Chamas Yedeichem Tefalesun"?
Rashi: In the land, you press down [on the scale] the Chamas of your hands, until it is a great weight.
Radak: The Chamas that you do with your hands, you publicize it in the land, and justify it to people with strong claims, as if it was done properly and straightly.
Malbim: Refer to 28:2:3:1.