Forgiving bows are ones that don't absorb form flaws of the archer meaning that they'll forgive your mistakes more than one that is "touchy".

Spine is measured in hundredths of inches of shaft deflection with a one pound weight hanging in the center of a 28" span of arrow shaft. It's a measure of how much or how easily a shaft bends.

Spine consistancy is a measure of how much variation there is amongst a given dozen shafts of the same manufacture.

What I think you mean by arrow tolerance is how broad a range of spine tolerance a given shaft lets you shoot across (as in a given 28" shaft being able to be shot over a 30# weight range rather than a 15# range) but I'm not sure on that one since I haven't heard it used popularly.

Broadhead alignment is how true the center line of the broadhead is to the center line of the arrow. If the broadhead is slightly off it will tend to make the arrow act as if it were bent in the direction the head is off (won't fly true). If they are true to one another you should be able to spin the combination on end with no discernable wobble in it.