Glad you asked I just finished making drawings in Solidworks so I should be able to help.
1. If you are referring to Keeper Plate item 11 (zone 1A) then yes .062 or 1/16" will do.
2.That symbol denotes the depth of the hole. In this case all the way through. The .75 is an error. The drilling and reaming needs to be done as a single piece after the slitting. If slitting is not done before ... the hole will not be concentric or the correct diameter.
3.The missing length (left of the .282) is not critical. So what I did is measured it (on the drawing) and scaled it up, I came up with .3 . So the overall length is: .3 + .282 +.125 (radius given from the hole to the edge) = .707 . Note that .707 is not the important dimension the individual ones are with the .3 least important.
Just as a note I found a lot of missing measurements ... and scaling up was the way I got the answer and most were not critical .. kinda left up to the builder.
Except one on the frames ... which I will go into later.
Hope this helps,