1) The ignition lamp should come on when the key is switched on and go out when the generator output is sufficient to charge the battery or run the electrical system. If it stays on then either the generator/regulator output is lower than the battery voltage or the light is wired wrong.
2) Would you ever really want to dim the panel lights on a Lucas system? Actually, you can bypass that switch without any negative results.
3) I don't know or remember what year your car is but if it has the voltage stabilizer then it probably has the later fuel gauge which does require the stabilizer. If you have the earlier gauge then you will not use the stabilizer. Also, the tank sending unit is different for the two gauges.
4) I don't have a bugeye ignition/light switch to refer to but my bugeye wiring diagram shows the following.
Post A gets a brown/blue wire from A1 on the regulator. Post H gets a blue wire to the headlight dimmer switch. Post gets a white wire to the ignition warning lamp and a white wire to A3 on the fuse block. Post 5 gets a red wire to the panel light switch and another red wire to a connector that eventually feeds the side Lights (parking lights), tail lights and tag lamp.
5) According to Lucas practice, the switch should have those posts labeled. If not, you can experiment some with your continuity tester and determine which is which. Again, according to my diagram, when looking at the back, post 10 is top-left, post 5 is top-right, post H is bottom-left and post A is bottom-right. The "S" on the bezel indicates "Side Lights" or parking lights. Enjoy.
Bayless
Never express yourself more clearly than you can think
'48 Prefect
'67 Sprite (project)