UFS GPT drive, ExFAT and UFS overlapping partitions

I'm in a pickle.

I have a FreeNAS system that I backed up to an external USB drive. I first formatted the drive on my Mac with the Disk Utility, and just created an ExFAT partition taking the entire drive, GPT partition table layout.

Later, when I realized ExFAT didn't seem to be well supported, I found a blog post recommending the following steps, which I think are the ones I wound up using:

gpt destroy /dev/da1  # Didn't work for me; nothing to destroy
fdisk -BI /dev/da1  # Format the external drive: one huge partition, bootable
bsdlabel -wB /dev/da1s1 # Write standard (bootable) disk label to the 1st partition
newfs -O2 -U /dev/da1s1a  # format the partition with UFS2 and soft updates

All worked fine, and I can mount and use the UFS file system at /dev/da1p2 on multiple FreeNAS 9.10 systems (FreeBSD 10.3).

However, if I plug into a Mac (using Disk arbitrator to mount read-only), an EFI and ExFAT file system show up. I'm afraid of running an incremental backup again until I fix that, and it took days (USB 2 only on the FreeNAS box) for the full backup.

Any clue how I can fix up the partition table? Thanks in advance.

Here are the outputs from gpart and fdisk:

[[B]root@freenas[/B]] [B]~[/B]# gpart show da1
=>         34  23441768381  da1  GPT  (11T)
          34            6       - free -  (3.0K)
          40       409600    1  efi  (200M)
      409640         2008       - free -  (1.0M)
      411648  23441354752    2  ms-basic-data  (11T)
  23441766400         2015       - free -  (1.0M)

[[B]root@freenas[/B]] [B]~[/B]# fdisk -v da1
******* Working on device /dev/da1 *******
parameters extracted from in-core disklabel are:
cylinders=1459182 heads=255 sectors/track=63 (16065 blks/cyl)

Figures below won't work with BIOS for partitions not in cyl 1
parameters to be used for BIOS calculations are:
cylinders=1459182 heads=255 sectors/track=63 (16065 blks/cyl)

Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 238 (0xee),(EFI GPT)
    start 1, size 4294967294 (2097151 Meg), flag 0
beg: cyl 1023/ head 254/ sector 63;
end: cyl 1023/ head 254/ sector 63
The data for partition 2 is:
The data for partition 3 is:
The data for partition 4 is:
No, it will not. You're destroying the partition table, effectively clearing the disk.