How come almost every time I do single engine on tail my plane behaves like slides running off the hill? Once I increase speed a little it's nose dips left or right despite landing gear still touching (and not willing to part with) the asphalt. At this point it is almost impossible to control the vessel and I crash.

Any routes around this problem? I want to make smaller planes for kerbin surveys, but this prevents me from even going SSTOs. I'm sick with doing overly huge wings in order to increase chance of taking off before i meet the ground.

How are your aerodynamics? You have to consider that in the scale of things, why the 747 or airbus is designed the way it is. The engines aren't on the tail. They're on the massive wings.