Upgraded to High Sierra, used Disk Utility, now Windows 10 won't boot

Macbook Air Mid-2011

Perfectly working state this morning:

Windows 10 x64 (upgraded in place from Windows 7 x64 which was created using standard Bootcamp steps in 2011, the upgrade was 3 years ago and was using standard windows process without having to mess with Bootcamp or do anything special).

Windows is the primary OS and machine has been running fine for years. Today I boot into OS X (I do this once a year for updates etc) and install High Sierra and to make some space, I use Disk utility (and do NOT touch the Windows partition), OS X only.

High Sierra successfully installs but when I try to boot back into windows, it just shows a white screen. Booting into OS X is working fine.

The Bootcamp partition still exists and is visible but the MBR is gone or GPT corrupted.

Contacted Apple Support online and they initially stuck with High Sierra isn't compatible with your device (wrong!), Hung up, called again and this time they redirected me to Nerdr article steps (http://nerdr.com/bootcamp-partition-lost-repairing-mac-partitions/) after the initial diagnostics that took an hour. I realise those steps were a mistake. Went to the Apple Store and they said they couldn't help with Boot Camp issues and that it looked like it was a High Sierra issue not Disk Utility (since High Sierra "moves stuff around"). We also tried to understand (but did not implement) couple of other threads where the issues were solved by Christopher Murphy and Loner T, but it was tough to figure out since some of the instructions seemed different:

Repairing Boot Camp after creating new partition

Windows 7 bootcamp partition not bootable after updating to 10.10.3

Repairing Bootcamp after resizing partition

Bootcamp not bootable after partitioning

Bootcamp Partition not bootable after resizing partition on HD

Repairing Boot Camp after creating new partition

Had too many doubts about those. Loner T made it clear not to follow Nerdr instructions but sometimes fdisk was used (built in?) whereas other times gdisk was.

System integrity is already disabled (followed Apple store person's instruction though they couldn't do it themselves coz not allowed). However sudo 'anything' always gives 'command not found' in the recovery terminal.

I'm tech literate and will follow instructions (unfortunately even when they are wrong) but am entirely unfamiliar with OS X and out of my depth here. Have used terminal in Linux and Cmd/Powershell in Win so willing to try anything at this point. I'd post the results of diskutil list but I have no idea how to copy it off of the Recovery and paste here.

OS X still boots fine and Bootcamp partition still exists. I really need to recover this (its not just Data but 400 tabs in browsers with Data I was working on that can't easily be copied).