Keep pushing your faction's influence up. It won't hurt if your faction is higher, it should actually make the war more likely. Try to get it over 70%.
However, don't let the controlling faction get too close in influence to any other factions. but this is unlikely with the numbers you have described.
There are two ways of triggering a war. One is to equalise the influence levels of two factions, the other is for a faction to get over 60-70%. So you are doing it right.
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What maddavo says about the state of the controliing faction in other systems is correct. Check in galmap for the faction states of the nearby systems. If this faction (or your one) is in a conflict or election in another system you may need to take steps to end the war. It won't hurt your efforts in your system to help your opponents in another system.
Thanks guys.