Inventor 2014 sketch constraint issues

I think these would all fall under the topic of sketch constraint issues, so here goes.

1-The big one, is there a way to stop Inventor from assuming I want to sketch an arc instead of another line segment because I am too hyper with my mouse? I use a trackball (Logitech M570) so if I don't let go of the button fast enough I get an arc instead of a line, which is annoying. Is there a setting to permanently disable this feature since I only want to create arcs from ribbon or with right click customization? Is there a setting for click speed in Inventor that could be adjusted?

2-When in sketch mode, sometimes lines etc. snap to bizarre geometry that is completely unrelated and beyond the limits of what can be seen on the screen. I see there is a Sketch\Constrain\Constraint Options button that looks likely, but I can't toggle it off and save changes, the OK button greys out when I untoggle "all geometry". Is there a way to limit the amount of geometry Inventor looks at when setting constraints in sketch mode? "Touching" the desired line or whatever and then moving in approximate direction (ex. putting a line parallel to another) sometimes works but if there is too much geometry in the sketch it seems Inventor freaks out and just puts constraints willy-nilly.

3-Lastly, I think this is related to Item 1. Sometimes when I try to draw another line (or whatever) the start point winds up being a slight and arbitrary distance away from the point I was trying to snap to. I'm guessing I moved the mouse too quickly w.r.t. releasing button? Click speed setting somewhere?

Thanks for the help!