Não sei se isso é útil, mas aqui estão os resultados do touchpad no meu Dell Latitude E6420:
user@computer:~$ xinput --watch-props 12
Device 'AlpsPS/2 ALPS DualPoint TouchPad':
Device Enabled (139): 1
Coordinate Transformation Matrix (141): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
Device Accel Profile (262): 1
Device Accel Constant Deceleration (263): 2.500000
Device Accel Adaptive Deceleration (264): 1.000000
Device Accel Velocity Scaling (265): 12.500000
Synaptics Edges (266): 300, 1700, 210, 1190
Synaptics Finger (267): 12, 15, 0
Synaptics Tap Time (268): 180
Synaptics Tap Move (269): 107
Synaptics Tap Durations (270): 180, 100, 100
Synaptics ClickPad (271): 0
Synaptics Middle Button Timeout (272): 75
Synaptics Two-Finger Pressure (273): 141
Synaptics Two-Finger Width (274): 7
Synaptics Scrolling Distance (275): 48, 48
Synaptics Edge Scrolling (276): 0, 0, 0
Synaptics Two-Finger Scrolling (277): 1, 1
Synaptics Move Speed (278): 1.000000, 1.750000, 0.081934, 0.000000
Synaptics Off (279): 2
Synaptics Locked Drags (280): 0
Synaptics Locked Drags Timeout (281): 5000
Synaptics Tap Action (282): 2, 3, 0, 0, 1, 3, 0
Synaptics Click Action (283): 1, 1, 0
Synaptics Circular Scrolling (284): 0
Synaptics Circular Scrolling Distance (285): 0.100000
Synaptics Circular Scrolling Trigger (286): 0
Synaptics Circular Pad (287): 0
Synaptics Palm Detection (288): 0
Synaptics Palm Dimensions (289): 10, 100
Synaptics Coasting Speed (290): 20.000000, 50.000000
Synaptics Pressure Motion (291): 15, 80
Synaptics Pressure Motion Factor (292): 1.000000, 1.000000
Synaptics Resolution Detect (293): 1
Synaptics Grab Event Device (294): 0
Synaptics Gestures (295): 1
Synaptics Capabilities (296): 1, 1, 1, 1, 1, 1, 0
Synaptics Pad Resolution (297): 1, 1
Synaptics Area (298): 0, 0, 0, 0
Synaptics Noise Cancellation (299): 12, 12
Device Product ID (257): 2, 8
Device Node (258): "/dev/input/event7"
Property 'Synaptics Off' changed.
Synaptics Off (279): 0
Você não mencionou se o touchpad funcionou corretamente no Windows. Se você ainda não verificou, provavelmente deve verificar isso para descartar um problema de hardware. Se funcionar bem no Windows, suponho que você deva mexer nos parâmetros. Se você encontrar algo que funcione, responda à sua própria pergunta e aceite a resposta para ajudar as pessoas no futuro. Boa sorte.