How can I properly remove Linux and resize the partition if it's showing FFFFFFFFFFFF-FFFFF-FFFFF without turning off my Macbook?
Download and install gdisk.

After downloading, you can remove the quarantine by entering the following command.

xattr -d com.apple.quarantine ~/Downloads/gdisk-1.0.4.pkg


Enter the commands given below.

sudo gdisk /dev/disk0
t
2
af0a
w
y


You can also use the gpt command, but gdisk has the advantage of being atomic. In other words, no changes are made to the GPT until you enter the y command.

If you want to try using the gpt command without first booting to macOS Recovery, then here are the commands. I warn you this might cause the computer to hang.

sudo -f gpt remove -i 2 disk0
sudo -f gpt add -i 2 -b 409640 -s 1796865488 -t apfs disk0