Partition that I use for data won't automatically mount after reboot

[Aragorn]

See if this can help you.

What else can be done to change my own partition permissions?

Welcome to the forum! First of all, the partition in question has a vfat filesystem on it, and vfat is not a UNIX-compatible filesystem. It does not store file ownership and permissions, so the permissions are faked in the kernel’s virtual filesystem layer at mount time and apply to the whole filesystem. They cannot be altered. Secondly, if you have Fast Boot enabled, then Windows will not properly shut down its filesystems, and then the Linux kernel will interpret this as if …

Note: This was written for a member with a FAT-based partition. If yours is NTFS, then see…

man mount

… for the correct mount options.