I wish had more time to offer a proper response but I realize that we are currently at the peak and you need some information now.
When I do DSLR astrophotography with a camera lens (no telescope), I'm usually shooting using an f/2 lens (at f/2) ISO 800, and typically 1 minute exposures. But I'll also shoot some shorter exposures (for HDR combination) and some of those exposures will be as short as 1-3 seconds depending on the subject.
That aside, since your 18-55mm lens is probably a variable f/3.5-5.6, I'm going to guess that your wide-open aperture is f/3.5 and that this is only available if you are at the 18mm focal length. Given these assumptions, I'll assume you will plan to use 18mm f/3.5.
Your Nikon has a crop-factor of 1.5x. That means if you use the 500 rule, it's
exposure-duration = 500 ÷ crop-factor ÷ focal-length
So for you that's
500 ÷ 1.5 ÷ 18 = 18.5
You can't accurately make an 18.5 second exposure so you'll likely set your camera to a 15-second exposure. You should also cheat it up a bit to a 20 second exposure.
I normally find I get good sky exposure with 1 minute at f/2 and ISO 800 and I get away with this because I have a tracking head (I have a Losmandy StarLapse head -- which is no longer sold. These days the Sky Watcher "Star Adventurer" head or the iOptron "Sky Guider Pro" head are the popular models.)
You'll need to adjust ISO to compensate for your shower exposure duration... in this case, doubling the ISO to 1600 (from my 800) would compensate for going from a 30 second exposure to a 15 second exposure. But we also have to compensate for your f/3.5 focal ratio (vs. my f/2). This would get you to roughly ISO 5000.
My guess is that using ISO 5000, f/3.5, and 15 second exposure durations will probably be pretty close.
Make sure you understand the nuances of your interval timer.
I usually use a computer (via USB connection) to control my camera, but I do have a physical wired-remote with an internal timer and my camera has a built-in interval timer (via the menu system). They all work a bit differently.
When I use the physical interval timer, it assumes the camera is in Bulb mode. The interval timer is programed for
- The delay before activating (usually I set this to zero since I am not touching the camera to trigger the shutter)
- The number of frames I want to capture (e.g. 100)
- The duration of a single frame (e.g. 15 seconds ... or 1 minute, etc.)
- The wait-time AFTER the shutter closed from the previous frame BEFORE beginning the next exposure.
The main message to the above description is that the "interval" in the case of this specific timer, is the time between the END of one exposure and the START of the next.
If I use the camera's internal interval time (it's not a Nikon so it's likely not the same), the built-in timer is ... not as smart.
- The number of frames
- The time interval between the START of exposures.
This timer doesn't care about exposure duration. You have to work out the math on your own. E.g. if the exposure durations are 15 seconds and I set an interval of 15 seconds it's probably that I'll have dropped frames because the camera wont quite be done and ready for the start of the next exposure when the camera tries to trigger the shutter. So for this particular timer, I have to pad... e.g. suppose I set a 20 second interval. That would give the camera 15 seconds to take the shot and a 5 minute padded buffer time until the next shot begins to make sure the camera is ready (and sure I could probably cheat that down a couple of seconds shorter).
There is a decent article on PhotographingSpace.com on Meteor Shower photography. You can find it here: https://photographingspace.com/beginner-meteor-photography/