There is really no defense to converting legal sep decree to dissolution decree. Either way, you will have to bring a motion to convert legal separation to dissolution. Prepare the motion and Order you want signed (converting), send him a Note For Motion Hearing setting a date and time when it will be present in Ex Parte. File motion and note for hearing with court and show up at hearing with Order you want judge to sign. If ex signs Order before then, take it to Ex Parte and have it entered.
Each county has a Family Law Court Facilitator who can help you. This is usually free or minimal cost.
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