In most states, and under federal banking laws, you are not allowed to withdraw funds from accounts unless:
a) you are an account holder OR a joint account holder OR
b) an authorized user or authorized signor on the account
You are neither. There are some exceptions if there is a power of attorney in place. However, powers of attorney have very specific triggers as to when they are valid and most of the time there is a need for incapacity or unavailability.
While you may have a MARITAL right to the funds in the account, you do NOT have a right to access the funds from the bank itself. Look at it this way. If your marriage has a net worth of $100,000 and $20,000 is at Bank of Husband in only his name, the $100k is still marital property for the divorce court to divorce. However, only the divorce court OR Husband can access the Bank of Husband to get at the $20k. If you were to access "Bank of Husband" you would be committing bank fraud. There is a difference between being entitled to the general idea of money and being entitled to that exact money.
Your first round of questions were about what your options were, legally, for getting financial support from the courts. The courts aren't going to let you log in under husband's name. Read the link I sent you over the weekend to see if any of your history with your husband or your 13-year-old son (restraining orders can be issued to protect step children too) supports a protective order. If so, that is your quickest way to have a court consider ordering financial support against your husband's wishes. The court can also award you the residence and put him in your apartment. The Court hates displacing children.