Chems, one of the first things you could to try to do before deciding on your door gap is have the wood at the correct moisture content for the environment it will finally reside in?
Have you taken any measures to control your workshop environment?
First thing you said when you asked the question was, "you fit your test door with a 1mm gap and now it's catching without any paint".
What is that telling you
The answer is the wood has swollen
Why has this happened, well it's taken in moisture from environmental changes and swollen to fill the original 1mm gap.
You first need to try to stabilise the door and frame. If you have no heating in your workshop and it's open to environmental changes (draughty with maybe open doors/windows) then you need to take some steps to cure this. You need to control your workshop environment to some extent to stand a chance of maintaining the correct gap in your door.
Some people take a sample moisture reading from a piece of wood in the location where the final piece will reside using a moisture meter, in your case a test reading from a piece of wood in the kitchen. They then use this reading to condition the wood they are working on to the same moisture content as the final environment (kitchen in your case). If you can control this process then there is far less chance of end product movement when it is installed in it's final location.
Here is a web link to a description of moisture meters:http://www.popularwoodworking.com/ameri ... ure-meters
So my advice would be to try to control your workshop environment to bring some control over the moisture content of the wood you are working on and condition the wood to the correct moisture content for the final environment, then take it from there.
Hope this makes some sense.