Only 4 or 5 attempts? That's jolly good
It always takes me numerous iterations. It's not the method of moving the points that's the problem, it's the way they like to shift as you tighten the screw...
As regards powering an electronic ignition unit without disturbing the armoured cable... this circuit ought to work, though I haven't tested it.
30 is the live feed to the ignition switch.
54 is the switched live for everything except the coil itself.
50 is the starter control connection.
The relay is a boggo Halfords unit.
The capacitor is to keep the relay energised during any possible hiatus between it receiving a feed from 50 and a feed from 54 as the key rotates. The value 1000uF is a "safe guess". It may work with a smaller value; it may even work without it.
Diodes and capacitor can be obtained from Amazon or ebay probably more cheaply than the minimum order charge from one of the usual electronic component suppliers.
The fuse should be chosen to suit the needs of the electronic ignition module. 10A ought to be OK.