Honestly, the switch between the two tests is very forgiving as you have seen from your result.
It wouldn’t take you more than a week to reconfigure your brain maybe two weeks.
So I think you have time, 2 to 3 weeks to make a difference in quant. I don’t mean overall but in specific topics and if you can see improvement, I would proceed but if you are not improvement, you can try the GRE back door.
My recommendation would be to start with creating a list which should take you 10 minutes: what makes you uncomfortable or an easy in quantity? Where is the soft spot?
Make a list and then target one of them and honestly targeting one of them should not take more than a couple days. It sounds like you have a proven track record and you know how to study.
One aspect to set your expectations and the area that a lot of people underestimate is GMAT is a test of nuance. It’s a collection of a lot of little rules and little trip wires that you have to keep in mind and so if you prolong studying over four or five or six months, you start losing those.
Another score killer is not lack of knowledge but rather timing where people spend way too much and then are forced to guess. If this is you, this will be the biggest easiest fix but my guess it’s not unfortunately.
Also now that you’re not in college, studying at night after work is really not ideal and while you do what you have to do, you also need to be honest with yourself - did you just watch this video or did you actually learn something. Sometimes it’s hard to tell but my recommendation is taking a daily quiz at the end of every topic or chapter and for you I’d recommend take 10 questions only within the topic you have just covered and aim to get a mix of easy medium and hard and somewhat equal proportions and hit at least eight out of 10 correct and preferably nine out of 10 .