Multimeter across Power Line voltage varies wildly
EMI filter is for fairly high frequencies (that you wouldn't pickup with your multi meter anyway) but might be a good idea to have one as well.


You can increase the 470uF cap at the input, but you also need to add some good ceramic cap, as electrolytic are not good at high transients. Add a (or several) 10uF ceramic cap in parallel to the 470uF cap close to the mos and coil, keep the electrolytic cap far away near the rectifier. 
Use big traces between the ceramic cap and the mos / coil.
Then you can filter the input to avoid injecting noise back into the network with an inductor, place another electrolytic cap and place the coil between them as a filter.








simulate this circuit &ndash; Schematic created using CircuitLab