You can write to hdb and appeal. They can be quite flexible about some things that i knew through a friend.The only problem will be if you decide to buy another flat from hdb directly. I suggest you write to or call hdb and ask.
You can file for immediate divorce with proof of adultery. Might be interested in the following taken from Singapore law society website
Judicial Separation
If you wish to live apart permanently but do not wish to commence divorce proceedings for various reasons, then you may make an application to Court for judicial separation.
A Judgment of Judicial Separation granted by the Court does not allow you to remarry. Your marriage has not been dissolved. However, you would be entitled to similar claims as in a divorce, e.g. custody, matrimonial assets.
Nullity
You may apply to Court to annul your marriage in some circumstances, for example:
if at the time of your marriage, your 'spouse' is already married;
your "spouse" has refused to consummate the marriage;
the marriage has not been consummated because you or your 'spouse' is incapable of consummating it;
if at the time of your marriage, your 'spouse' is suffering from venereal disease and you are not aware of this.
The above grounds are not exhaustive. Please consult a lawyer if you require further information.
Deed of Separation
You may wish to be separated from your spouse for a period of time before you decide on a divorce. In this case, you may sign an agreement called a Deed of Separation which will set out the terms and conditions governing the relationship between you and your spouse during the period of separation. It would be advisable for you to consult a lawyer to draft the Deed of Separation.
You may decide to reconcile with your spouse after signing the Deed of Separation. Alternatively, you may proceed with your divorce after 3 years (if your spouse consents) or 4 years (if your spouse does not of separation).
Legal Aid Bureau
If you cannot afford a lawyer, you may apply to the government-run Legal Aid Bureau for assistance. The Legal Aid Bureau is situated at:
45 Maxwell Road #08-12
The URA Centre, East Wing
Singapore 069118
Tel: (65) 1800 325 1424 (toll-free)
Fax: (65) 63251402
Website:
www.lab.gov.sg
Please note that you have to pass a Means Test to qualify for assistance from the Legal Aid Bureau. The Means Test is a procedure to ascertain your financial position.
But, pls do consider carefully as children are involved.
Website:
http://www.lawsociety.org.sg