I haven't even upgraded the first laser on the Mole yet, haven't had enough time in the game and most of my time has been spent trying to figure out what's up with my T16000M. It often spins my ship counterclockwise when I'm turning to the right. I thought it was a game problem, but no it's actually getting the signal to rotate from the hardware.You're got the math correct.
I have encountered rocks(very rare) that could not be cracked by a Helix. These usually have 4-5 different minerals inside of them and while the rock may have only been a 6K mass or so rock with 'low' resistance it still took 2 full power helix heads to break it. Why? I don't have any proof but I suspect that each mineral inside the rock has a specific resistance factor to it. Combined with the overall mass of the rock the laser sometimes won't make a dent unless you bring a 2nd
It doesn't help that I had to hunt all day yesterday for a philips screwdriver. I'm not sure if I'd get more mileage from upgrading the joystick, or the kid that keeps borrowing tools and not putting them back.