There is no real spec for the distance, but 1/8 is rather small. I like to see the linkage adjusted just as close as possible without the throwout bearing running all the time. If you do encounter times you can take off in 2nd, go ahead and do it. The disc will usually get better as it it wears in.
Back when these things were new, we didn't have the traffic we have now and we are able to give them more time. I wouldn't make a habit of it, but in a tight situation, using 2nd to stop the driven gear is probably the best solution. Another way to do it if you can is to pop it into 1st while the vehicle is still moving a little bit instead of waiting until you are at a dead stop.
I have put thin washers for shims between the pressure plate and flywheel on some real bad ones.
But when it gets down to it, it has always been a problem. That is why Saginaw put synchronizers on 1st gear in 19663
