You can burn heated WVO with a pressure nozzle but it is not just effected by the micron filtering level. The oil will also coke up or get gummy inside of the nozzle after a period of running and will require frequent nozzle changes. Cleaning of a pressure nozzle is not very effective, especially the small firing rate ones like yours. Fin filtering won’t help the coaking or gummy deposits.
I suspect pre-purge and post purge will extend the time that it takes to foul the nozzle since the post-purge will cool the nozzle at shutdown. Since I am using air atomization, I have not done any experimentation with post purge on a waste oil pressure burner but it helped with my Riello BF3 on HHO, extending cleanings to only once every two years. It also extended time between cleanings on my air atomized waste veggie oil burners.
Gaskets will last longer on WVO than they do on biodiesel. Some filter elements are not compatible with waste oils. Paper filters intended for water are often damaged by WVO.
Your firing rate is almost identical to what I was using on HHO with a Riello in a Buderus boiler. My siphon nozzle burner is using a .2gph siphon nozzle with 10-13psi air pressure and from 3” lift to 8psi oil pressure depending on the firing rate that I want.
Your oil supplier is probably filtering the fuel to 10 microns rather than 1 micron but even if they are, you still need to filter the oil just before it goes to the burner to remove contaminants from the tank. The preheater will need to be between the pump and the nozzle since the pump shouldn’t see oil much over 150 degrees F.
Spray angle with a siphon nozzle is a real problem since they only come in one pattern, approximately equivalent to a 25 degree solid. Getting the wider flame angle requires retention head design to force more swirl. A waste oil burner, especially a pressure nozzle one, is more effected by short cycling than a HHO burner so boiler aquastat/controls settings that extend run time (I.e.wider differential setting) will help. And as always recommended, get a spare burner to modify rather than modifying the one that you are already using.
The information about maximum pump temperature is useful to me. I’ve been trying to find an official manufacturer’s specification on this. Where did you find this information about 150 degrees or so for oil temperature at the pump? Do you know the specified maximum temperature for a fuel oil pump? Is this maximum temperature fuel oil related or is it related to the materials of which the pump is constructed?