The dimmer circuit is hopeless.
The pot is too high - 470 k in parallel with 220 Ohm will make little difference. And both ends should not be connected together.
But if you use a lower value pot, say 1000 Ohm, then it would have to be a high power wire wound type in order to dissipate the power.
Do you want to be able to vary the brightness with a pot or do you just want to reduce it permanently?
If the latter, then you could change all of the resistors for larger values.
If the former, then use either option 2 or 3 suggested by Hero999.