Welcome back! For the grass problem, you could always turn it off completely, but other than that there isn't much else you can do. As for mouse sensitivity, you could always try changing the options for your mouse in the Windows Control Panel (assuming you're using Windows). Unfortunately, there isn't much you can do for the rest of your problems.
My guess as to the biggest reason that these are still problems years after launch is due to the heavily modified pre-alpha Hero Engine the original devs used to create the game. And since an engine update/change is very unlikely, I doubt that these issues will be corrected anytime soon.