Hi Petra,
For your config "2. create custom condition for custom AOT and assign it to the event handler type", I am sure you mean't assign custom AOT to Custom EH Type. Isn't it?
Then during FU/FO create/change, see if the flow is through you custom AOT by putting a break point. If it hits the breakpoint then you should be able to create custom Event Handlers.
So, to your question, custom AOT condition on your custom EH type should work provided right BPT is there.
Also, as Affan said, disable/remove Event Manager from standard AOT. If they have to be there, make sure your sequence is right and/or there is no check on the "Stop AO Determination" on the standard AOTs.
Otherwise, your config seems good to create custom EH type ( double check you Assign Profile to Mapping ).
Let us know if you still don't see Custom EHs.
Thanks.