It sounds like you are reading the RPM, not the dwell angle off your meter.
As for the point gap, I looked it up on the CD, and they don't give a gap, only a dwell angle of 47 degrees.
You adjust the dwell angle by changing the point gap - by turning the distributor you are changing the timing. I suggest that you get the dwell right, and then set the timing with a timing light. The CD says 10 degrees BTDC.
Carbon on the plugs means you have a rich fuel mixture. It could be from several causes. I would get the gap and timing sorted out, then take the car for a drive that allows it to get fully warmed up. Then pull a plug or two and see what the carbon situation is.
If you need the dwell and timing procedure, send me an email.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe