Timing and Hot Running

Help please with my 1972 750 combat commando which is now running but with a few problems. The bike takes 5 to 10 kicks to start and then after a few minutes the choke can be turned off and it will idle around 1000 RPM or just below. This seems ok but engine becomes very hot with the primary side being hotter than the timing side based on pipe bluing (see photo). Also the primary side does occasionally pop/bang when revs are decreasing. I have included a picture of the plugs; primary side seems to be ok or is it too light and hence weak? The timing side plug is showing sights of running rich so I believe?

Also the revs sometimes stick at around 1500-2000 RPM and is reluctant to return back to an idle. To get it back is either further twisting of throttle or waiting a short while or stopping the engine and then restarting. The revs sticking I believe is attributed to the cable going from the junction box to the primary side carb being damaged. I also found the needle on the timing side carb to be bent so new cable and needle is on order.

So to address the running hot issue I have now started to look at the basics around points/plug gap and timing and my initial questions are

1) To set the gap on the points I have loosened screw A as shown on the attached photo and then used screw B to increase/decrease gap. Is this correct as itâs different to the way the workshop manual describes based on my reading of the manual.

2) I have followed the basic timing process in the manual but when I move the engine backwards using the rear wheel to 28 degrees then respective contact breaker is close to the point of opening but if I continue to move the engine backwards to the point that the contact point is about to open then the marker on the rotor is somewhere back before 10 degrees. I understand that the accuracy of the marker on the rotor cannot be relied on so what is the best way of progressing with the timing? In the attached picture you will see a photo of the marker at 28 degrees and a photo of the points. The timing was based on the left cylinder (primary side) with the left side contact breaker being the one which is meant to start to open.

3) I moved the cam to advance it and this took it very close to the point of opening. When I released the cam, should the cam spring back to the original position, this one did not? Do I need to put a new spring on the advance retard unit?

All advice/guidance welcome and if someone is based near Maidstone Kent and willing to help with the timing that would also be most welcome.

As always many thanks in advance for all input given

Neil