I'm using a wacom pen. It happens to often that I'm trying to grab a handle or point in the viewport and houdini deselects it instead.

Is there a way to increase the distance at witch a mouse click will still select a handle or point instead of deselecting everything?

Try enabling “secure selection,” it's not the same as what you want, but should help prevent errant deselections.

Houdini Preferences / Handles / Pick Distance