I didn't like my X-T2 till I got one of the actually good lenses for it to be honest. The kit lens is pretty much just a lens that allows you to shoot on it when you bring it home. Is it a bad lens? no. Is it the lens that defines the entire ecosystem? No. You have a starting point, the X-T3 is great for video work as long as you know exactly what light situations you're walking into and prepared yourself accordingly. Also you might really want to get yourself accustomed to the camera especially if it's your first mirrorless after being in DSLR territory. The low light AF is pretty serviceable if you're allowing enough light to hit the PDAF sensor. If not, you're going to have problems. I pretty much natural lighted a wedding with the X-T2 and X-T3 to pretty much stress test them. If I can get this shot in a technicolor lighted dining area you can as well.
DSCF1081 by
Marcus Beasley, on Flickr
Also what and where are you trying to shoot? If you're in the dark nothing will work. Also you can get an adapter, but don't expect anything with AF. Nikon did not make their lenses easy to adapt or even worth adapting unless you want to manual focus or shoot nothing but portraits. I would know I'm dealing with that transition yourself. Depending on what they are they might not even be worth adapting to be honest...granted you do video work so it's worth shot.
I hope you kept the receipt for that 85. If not sell it on Ebay, they go like hot cakes if they're priced right. Also find the time to turn on the camera. A camera not being a camera is a waste of money.