Failed attempt to rebuild raspberry pi filesystem (ext4)

My raspberry pi failed to boot, and I tracked it down to being a damaged main linux partition.  I tried to repair the partition, but it didn't work.  This posts lists some of the things I tried for posterity.

• attached to other raspberry pi running raspbian
• was able to mount the boot partition
• was unable to moun the main partition
• was able to copy the main partition using dd
• command:  
  nohup sudo dd bs=4M if=/dev/sdc2 of=raid0/cape/2018-09-03_piB_main_partition.img conv=fsync &
• output:
  3795+0 records in
  3795+0 records out
  15917383680 bytes (16 GB, 15 GiB) copied, 3292.09 s, 4.8 MB/s
• attempted fsck.ext4 on the disk
• command:  
  sudo fsck.ext4 /dev/sdc2 
• output:  
  e2fsck 1.43.4 (31-Jan-2017)
  /dev/sdc2: recovering journal
  Superblock needs_recovery flag is clear, but journal has data.
  Run journal anyway<y>? yes
  fsck.ext4: Unknown code ____ 251 while recovering journal of /dev/sdc2
  fsck.ext4: unable to set superblock flags on /dev/sdc2
  
  
  
  
  /dev/sdc2: ********** WARNING: Filesystem still has errors **********
• from this stack exchange on unix & linux it appears that the attempts to write to the SD card are failing - probably need a new SD card
• attempted fsck.ext4 on image of filesystem  (seems possible based on this other StackExchange Unix & Linux)
• 1st made copy of image
• then command:  
  sudo fsck.ext4 2018-09-03_piB_main_partition_copy.img 
• output:  
  e2fsck 1.43.4 (31-Jan-2017)
  2018-09-03_piB_main_partition_copy.img: recovering journal
  fsck.ext4: Bad magic number in super-block while trying to re-open 2018-09-03_piB_main_partition_copy.img
  
  
  2018-09-03_piB_main_partition_copy.img: ********** WARNING: Filesystem still has errors **********
• find backup superblocks & attempt to use to repair:
• find backup superblocks - command: 
  sudo mke2fs -n 2018-09-03_piB_main_partition_copy02.img 
• output:  
  mke2fs 1.43.4 (31-Jan-2017)
  2018-09-03_piB_main_partition_copy02.img contains a ext4 file system
  last mounted on / on Mon May 28 19:03:51 2018
  Proceed anyway? (y,N) y
  warning: Unable to get device geometry for 2018-09-03_piB_main_partition_copy02.img
  Creating filesystem with 3886080 4k blocks and 972944 inodes
  Filesystem UUID: 16542ed2-1cc7-45ea-a49c-4d3213eab6a1
  Superblock backups stored on blocks: 
  32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208
• attempt repair using first backup superblock - command:  
  sudo fsck.ext4 -b 32768 2018-09-03_piB_main_partition_copy02.img 
• output:  
  e2fsck 1.43.4 (31-Jan-2017)
  2018-09-03_piB_main_partition_copy02.img: recovering journal
  fsck.ext4: unable to set superblock flags on 2018-09-03_piB_main_partition_copy02.img
  
  
  
  
  2018-09-03_piB_main_partition_copy02.img: ***** FILE SYSTEM WAS MODIFIED *****
  
  
  2018-09-03_piB_main_partition_copy02.img: ********** WARNING: Filesystem still has errors **********
• despite the error, was able to then mount, albeit with errors - command:  
  sudo mount 2018-09-03_piB_main_partition_copy02.img ~/temp/
• output:  
  ls: cannot access '/home/lahr/temp/bin': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/tmp': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/sbin': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/boot': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/home': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/mnt': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/root': Structure needs cleaning
  ls: cannot access '/home/lahr/temp/dev': Structure needs cleaning
  total 60
  d?????????   ? ?    ?        ?            ? bin
  d?????????   ? ?    ?        ?            ? boot
  d?????????   ? ?    ?        ?            ? dev
  drwxr-xr-x 111 root root  4096 Aug 22 18:27 etc
  d?????????   ? ?    ?        ?            ? home
  drwxr-xr-x  12 root root  4096 Oct 24  2017 lib
  drwx------   2 root root 16384 Feb 15  2015 lost+found
  drwxr-xr-x   6 root root  4096 Dec 18  2017 media
  d?????????   ? ?    ?        ?            ? mnt
  drwxr-xr-x   6 root root  4096 Feb 16  2015 opt
  drwxr-xr-x   2 root root  4096 Jan 11  2015 proc
  d?????????   ? ?    ?        ?            ? root
  drwxr-xr-x   7 root root  4096 Feb 16  2015 run
  d?????????   ? ?    ?        ?            ? sbin
  drwxr-xr-x   2 root root  4096 Jun 20  2012 selinux
  -rw-r--r--   1 lahr 1004    16 Nov 27  2017 srv
  drwxr-xr-x   2 root root  4096 Oct 12  2013 sys
  d?????????   ? ?    ?        ?            ? tmp
  drwxr-xr-x  10 root root  4096 Feb 15  2015 usr
  drwxr-xr-x  11 root root  4096 Feb 16  2015 var
• attempt cleaning with 2nd backup superblock - command:  
• attempt regular cleaning - command:  sudo fsck.ext4 2018-09-03_piB_main_partition_copy02.img
• lots of prompts for repairs; eventually chose "all" option
• still mounted with problems, ran cleaning above, was mounted, reported output:  

e2fsck 1.43.4 (31-Jan-2017)
2018-09-03_piB_main_partition_copy02.img contains a file system with errors, check forced.
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Block bitmap differences:  -41468
Fix? yes
Free blocks count wrong for group #1 (15656, counted=15657).
Fix? yes
Free blocks count wrong (3188435, counted=3069400).
Fix? yes
Free inodes count wrong (887659, counted=869921).
Fix? yes

2018-09-03_piB_main_partition_copy02.img: ***** FILE SYSTEM WAS MODIFIED *****
2018-09-03_piB_main_partition_copy02.img: 103023/972944 files (0.2% non-contiguous), 816680/3886080 blocks

• further fsck reported filesystem as clean - however, the mounted filesystem is missing /home and other critical directories.