Kernel module crash when reading system call table function address

I am studying rootkits and trying to hook the system call table. As i can already dynamically retrieve the table's address from /boot/System.map-$(uname -r), i traced and isolated the problematic part of the code into an independent, simpler module, shown below. It tries to retrieve and display the address of the kill system call, but insmod returns "Killed" on module load, which is an error provoked specifically on the emphasized line.

Kernel string: 5.2.0-3-amd64

Module:

#include <linux/module.h>
#include <linux/kernel.h>

typedef asmlinkage int (*sys_kill_ptr_t)(pid_t, int);

static sys_kill_ptr_t sys_kill_ptr;
static unsigned long *syscall_table;

static int __init lkm_init(void)
{
    printk("[+] LKM: init\n");

    // System call table address in /boot/System.map-$(uname -r)
    syscall_table = (unsigned long *)0xffffffff81c002a0;

    printk(KERN_INFO "[+] LKM: syscall_table @ 0x%p\n",  syscall_table);
    printk(KERN_INFO "[+] LKM: syscall_table @ 0x%lx\n", (unsigned long)syscall_table);

    /* Error */
    sys_kill_ptr = (sys_kill_ptr_t)syscall_table[__NR_kill];
    /* Error */

    printk(KERN_INFO "[+] LKM: sys_kill_ptr @ 0x%p\n", (void *)sys_kill_ptr);

    return 0;
}

static void __exit lkm_exit(void)
{
    printk("[-] LKM: exit\n");
}

module_init(lkm_init);
module_exit(lkm_exit);

dmesg:

[ 3708.343306] [+] LKM: init
[ 3708.343309] [+] LKM: syscall_table @ 0x000000004853bd64
[ 3708.343360] [+] LKM: syscall_table @ 0xffffffff81c002a0
[ 3708.343407] BUG: unable to handle page fault for address: ffffffff81c00490
[ 3708.343460] #PF: supervisor read access in kernel mode
[ 3708.343501] #PF: error_code(0x0000) - not-present page

dmesg (after a reboot):

[   86.822522] [+] LKM: init
[   86.822525] [+] LKM: syscall_table @ 0x0000000000248a4b
[   86.822644] [+] LKM: syscall_table @ 0xffffffff81c002a0
[   86.822757] BUG: unable to handle page fault for address: ffffffff81c00490
[   86.822903] #PF: supervisor read access in kernel mode
[   86.823005] #PF: error_code(0x0000) - not-present page

I have the following questions:
(0. Why does it crash and what can i do about it?)
1. Why does "%p" print a different value than that of "%lx"?
2. Why does "%p" print different values after reboots while "%lx" always prints the correct value?