Hi Bob, since your white engine had its carburetor fuel intake clogged up, it sounds like you are doing some good, even if it turns out not to be the diaphragm. Generally similar symptoms, probably.
Joe Carroll has converted a few B&S breaker-point engines to Magnatron, and posted about it on this site. You don't need to do anything with the points except disconnect the wire - they can sit there and open and close if they want to, nobody cares. I think I'd leave them there at least until you had thoroughly tested it with electronic ignition, so you are keeping your options open.
I don't know anything about the self-propel mechanism. We either need pictures, or for someone who is already familiar with it to join in here.
