Dimension lines, Push/Pull inconsistencies, Layout dimensions

I am baffled by what must surely have logical answers. Firstly why is it that when setting out a dimension guide (I assume I do it the same way each time) it sometimes puts in the measurement marker point and not the line? Also sometimes it will not present the line at all and when I change the view it does?
Also why is it with the push/pull command that sometimes it pulls and extends perfectly and at other times it pulls the face only and leaves a void behind? On the push/pull command as well I do not understand when say pushing a window opening through a wall and inputting the exact dimension it sometimes leaves the external face behind and sometimes does not in a wall that is the same thickness.
Finally in layout I have set to mm it reads as much out on the same wall thickness and measurement dimension locked to the same axis? I understood that the line was a theoretical line and had no width in reality if this is so, can this be true?

Sorry, I don’t understand what you wrote…Please try again.

Thank you for you very detailed response. As a learner advice from experts is very helpful and appreciated.
In answer
I now understand the issue with dimension line - thank you,
On the second point I wouldn’t know how to post a picture of it! However you may well be right re the graphics card. It is not up to spec according to the sketchup checker.
I will use control to override the push pull problem I have occasionally.
Again I will take your advice about trying to use the inferencing system more often and where possible.

As to the last point. If for example I draw in plan a wall say 100mm thick. The process might be to draw the first line in plan and a parallel dimension line 100mm off and draw a line on top which intersects with 2 equal end points and push pull the wall up. Alternatively use the rectangle tool on the dimensions line in plan to create a rectangle and push/pull it up. In either case then punching a window opening in and inputting 100mm - 95% time it works perfectly. Sometimes it leaves a face behind and if I redo it and input say 101mm it breaks he face and leaves a clear opening.

Without seeing an example, I can only guess. Could you upload a model in which this happens?

Most of the time what you describe would be due to you accidentally not placing things where you thought, which is easy to do particularly while you are learning. I’d recommend using the rectangle tool because it absolutely assures that the opposite sides are parallel and that the corners are square. And I’d type the length and width explicitly, as opposed to relying on a guide line for the opposite side. That way is faster and less likely to get an accidental error.

Thank you. As I was replying to you I was thinking in the back of mind that I would try to use the rectangle tool more following your advice on inferencing being more accurate and it would follow I assume for the rectangle tool. Years ago I had an early 2D CAD drafting background and now constantly have to refocus on the tools in Sketchup ( which are incredibly advanced from my 2D days) while thinking back to 2D presentation. I find the mindset for modelling and drafting quite different.