From my understanding, If you surrender before MOP its at 95% of the price you first purchased from HDB.
You can appeal to HDB for loan due to divorce and a young child. HDB is supposed to judge case by case basis for divorces.
If you get declined email the minister, or MCYS for support.
if you had the flat for a couple of years and very close to MOP, can still appeal to sell open market and then buy a smaller flat.