As for the second item:
Being quite a newbie to drools/jbpm stuff I might not have the right understand of things... but thinking about it: isn't it logical that every process proceeds if the condition described above resolves to true? It's just looking for a match in the knowledge base: a process with a variable "orderId" and an order with that id and tasksComplete being true. Of course there is only one match but it will fire for every process.
If there was a "then" part and it would depend on the "then" part which process to proceed then it could be done this way. But whithout!?