Using disk-manager on ext4 usb hard drive converted it to "stealth" FAT32

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I'm running jessie, and from boot-to-boot, and upgrade-to-upgrade my usb external HD link would either come up to the proper mount point using autofs, or the default mount points usb0,usb1, etc. After a recent upgrade, only the default mount points usbXX, etc. were produced, no matter how many times I rebooted. The usb drive was originally formatted ext4.

I decided to try to fix the mount point by using disk-manager, which gives the option to change the mount point for any given drive, even usb external drives. I selected my mount points and rebooted. I was dropped into single user mode with a mandate that I run fsck on the usb drive. One partition, of the two, passed clean, right away. The other was confounded with inode and block warnings. I accepted ALL of the fixes offered. At the end, fsck reported a clean FAT32!@$# partition@#$!!! What happened???

When I rebooted, the system dropped me back into single user because it couldn't mount the "fsck messed with" partition as ext4. Therefore, I went into fdisk, and changed the type of the partition from FAT32 to Linux. I also went into fstab and explicitly entered the UUID of the drive, and specified ext4 (I had never used fstab before with the external drive). Another reboot, and the system came up multiuser. I took a look at the files on the "fsck messed with" (fmw) partition, and they were all there. I then tried to use the fmw partition and I found that copying a file now took HUNDREDS of times longer than before. The usb drive partition that had a clean pass wasn't affected. Thus, the fmw partition had definitely been radically altered to a "stealth" FAT32 file system. I say "stealth", because one cannot use mount -t vfat /dev/sxx /mydir. If you try, mount claims that the FAT32 file system is broken. However, if I don't use the -t option, and remove ext4 specification from fstab, therefore letting mount figure out the file system on its own, the partition is successfully mounted as FAT32. File copy times then returned to normal. I feel like I'm on thin ice with this situation. One big mistake was running fsck, and not fsck.ext4 or esfsck. I was ignorant of those options before things went wrong.
Is there any way I can get back to a normal ext4 usb HD partition with normal read/write times? Not being able to manually mount the drive with an explicit -t vfat is especially troubling. Are there other -t options for variant FAT32 file systems not in the manual for "mount"?