I'll chime in as somebody who upgraded from a crop-sensor D7000 to a D750 2 years ago.
My motivation for buying into a full-frame body was less noise at high-ISO, capturing wider angle images with better lens options, and work with a narrower depth-of-field to isolate a subject more easily. These are all things that get compromised when working with the crop-sensor DX format. What DX does better is telephoto reach, like with wildlife photography.
That said, I can see where you might want lower-noise photos and wide angle field of view if you are doing interior real-estate photography. I presume you are doing it for some side-money, but you want to preserve your 10-24mm lens. I will speak from experience here. If you buy an FX body, consider the DX lenses to be something to forget. Yes Nikon includes a mode in the D750 for doing an automatic crop to allow a DX lens to work on it. But consider what that involves. Only the image in the center area of the sensor is used, the rest of the image is discarded. You turn a nice 24MP sensor into a crappy 10MP sensor. I suspect you will want the D5300 back when you look at the images.
Now if you are watching youtube videos a lot, as I have been guilty of myself, they more popular channels will start to make you feel like an amateur if you are not using a mirrorless full-frame body. And they will say you MUST have a 14-24mm f/2.8, 24-70 f/2.8, and a 70-200mm f/2.8 lens or else you kit will never make it. I say that is maybe the way for somebody shooting weddings and portraits as a main living, but even then it depends. If you have a personal style, there are certain lens ranges and designs you should have, but not necessarily another.
Let's say you gain an advantage with the full frame body for real estate work. Photographing your child's antics is something either a DX or FX format will do well. You are not really shooting telephoto from the sound of it currently. So I say it is not a bad idea to do the upgrade to FX. If you are trying to be forward-looking, the Z-mount mirrorless is the way. The D750 is out of production and has been replaced by the D780, so the new cameras are actually a year or so old at this point. Nikon is shifting away from F-mount, and is not devoting as much R&D toward that, if they have not gone fully Z-mount in the R&D lab already. The old DX lenses would need to go anyhow, so you might as well get the Z-mount lenses. I will say the F2Z adapter is still a good idea at this point since Nikon has been very slowly rolling out the new Z lenses. If you get a 14-24mm and a 24-70mm you will have the same field of view as your current lenses. Consider f/4 versions to save money, or try to get the f/2.8 14-24mm for the real estate work. The bigger disadvantage of a mirrorless body is the viewfinder will lag behind real life just a smidge. Not something you will notice or find problematic as I understand with just people subjects at normal range. But fast-action sports and wildlife at perhaps 150mm or longer and you can easily fall behind if you are tracking a subject like a bird in flight. Static or posed photos, the mirrorless has advantages. Like being easier to see the composition of a slightly dark room in the viewfinder.
If you cannot justify the cost of buying those new lenses, maybe now is not the time to upgrade. I have the benefit of a local camera shop I can shop at. I bought my D750 locally for only about $100 more than Amazon offered at the time. And I traded in a bunch of gear at the time of the sale and received more than $200 in trade value. I even kept my old D7000 and 2 DX lenses for it, it was an even older D80 and the less desirable lenses I traded-in. For that matter, consider KEH camera for selling used gear at. They even should have some used Z6 gear you can buy for a bit of a discount.